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An abstract of the article "Vaccine Enhancement Confirmed among Men in HVTN 503-S, Final Results from a Recall Study of Phambili Participants" by Zoe Moodie and colleagues is presented.

Controlled human malaria infection (CHMI) studies deliberately infect healthy participants with malaria to test interventions faster and more efficiently. Some argue the study design and high payments offered raise ethical concerns about participants' understanding of risks and undue inducement. We conducted baseline and exit interviews with 16 CHMI study participants to explore these concerns. Participants described themes including decision-making tension with friends and family, mixed motivations for participating, low study risks but high burdens, fair compensation, sacrificing values, deceiving researchers, and perceived benefits. Our findings do not support concerns that high payments limit understanding of study risks, but suggest participants may lack appreciation of study burdens, withhold information or engage in deception, and experience conflict with others regarding study participation. [ABSTRACT FROM AUTHOR]

An abstract of the article "To Use or Not to Use Clade Specific Vaccines: A Central Question" by Dobromir Dimitrov, James Kublin, Scott Ramsey, and Larry Corey is presented.

Introduction: Screening for G6PD deficiency can inform disease management including malaria. Treatment with the antimalarial drugs primaquine and tafenoquine can be guided by point-of-care testing for G6PD deficiency. Methods and findings: Data from similar clinical studies evaluating the performance of the STANDARD G6PD Test (SD Biosensor, South Korea) conducted in Bangladesh, Brazil, Ethiopia, India, Thailand, the United Kingdom, and the United States were pooled. Test performance was assessed in a retrospective analysis on capillary and venous specimens. All study sites used spectrophotometry for reference G6PD testing, and either the HemoCue or complete blood count for reference hemoglobin measurement. The sensitivity of the STANDARD G6PD Test using the manufacturer thresholds for G6PD deficient and intermediate cases in capillary specimens from 4212 study participants was 100% (95% Confidence Interval (CI): 97.5%–100%) for G6PD deficient cases with <30% activity and 77% (95% CI 66.8%–85.4%) for females with intermediate activity between 30%–70%. Specificity was 98.1% (95% CI 97.6%–98.5%) and 92.8% (95% CI 91.6%–93.9%) for G6PD deficient individuals and intermediate females, respectively. Out of 20 G6PD intermediate females with false normal results, 12 had activity levels >60% on the reference assay. The negative predictive value for females with G6PD activity >60% was 99.6% (95% CI 99.1%–99.8%) on capillary specimens. Sensitivity among 396 P. vivax malaria cases was 100% (69.2%–100.0%) for both deficient and intermediate cases. Across the full dataset, 37% of those classified as G6PD deficient or intermediate resulted from true normal cases. Despite this, over 95% of cases would receive correct treatment with primaquine, over 87% of cases would receive correct treatment with tafenoquine, and no true G6PD deficient cases would be treated inappropriately based on the result of the STANDARD G6PD Test. Conclusions: The STANDARD G6PD Test enables safe access to drugs which are contraindicated for individuals with G6PD deficiency. Operational considerations will inform test uptake in specific settings. Author summary: The glucose-6-phosphate dehydrogenase (G6PD) enzyme helps red blood cells work properly. When the body does not have enough of this enzyme and is exposed to oxidative challenges, including certain foods and medicines, red blood cells break down faster than they are made, causing hemolytic anemia. Diagnostics tools for this common condition have been limited but now, new point of care tests are available that can screen more people who are unable to access laboratory services. This is particularly important for the treatment of vivax malaria, where the only treatment options require G6PD screening before administration. This research provides an evaluation of the diagnostic performance of one such tool, the STANDARD G6PD Test (SD Biosensor, South Korea), based on extensive data from multiple studies. These data show that the test can be used to safely identify people with G6PD deficiency, which will help ensure they do not receive contraindicated medicines. The research also provides specific estimates about how this test may impact malaria case management and treatment options. [ABSTRACT FROM AUTHOR]

Background Sensitive molecular assays, such as quantitative reverse-transcription polymerase chain reaction (qRT-PCR) of Plasmodium 18S ribosomal RNA (rRNA), are increasingly the primary method of detecting infections in controlled human malaria infection (CHMI) trials. However, thick blood smears (TBSs) remain the main method for confirming clearance of parasites after curative treatment, in part owing to uncertainty regarding biomarker clearance rates. Methods For this analysis, 18S rRNA qRT-PCR data were compiled from 127 Plasmodium falciparum –infected participants treated with chloroquine or atovaquone-proguanil in 6 CHMI studies conducted in Seattle, Washington, over the past decade. A survival analysis approach was used to compare biomarker and TBS clearance times among studies. The effect of the parasite density at which treatment was initiated on clearance time was estimated using linear regression. Results The median time to biomarker clearance was 3 days (interquartile range, 3–5 days), while the median time to TBS clearance was 1 day (1–2 days). Time to biomarker clearance increased with the parasite density at which treatment was initiated. Parasite density did not have a significant effect on TBS clearance. Conclusions The Plasmodium 18S rRNA biomarker clears quickly and can be relied on to confirm the adequacy of Food and Drug Administration–approved treatments in CHMI studies at nonendemic sites. [ABSTRACT FROM AUTHOR]

Background: Developing a cross-clade, globally effective HIV vaccine remains crucial for eliminating HIV.Methods: This placebo-controlled, double-blind, phase 1/2a study (NCT02935686) enrolled healthy HIV-uninfected adults at low risk for HIV infection. They were randomized (1:4:1) to receive 4 doses of an adenovirus 26-based HIV-1 vaccine encoding 2 mosaic Gag and Pol, and 2 mosaic Env proteins plus adjuvanted clade C gp140 (referred to here as clade C regimen), bivalent protein regimen (clade C regimen plus mosaic gp140), or placebo. Primary endpoints were safety and antibody responses.Results: 152/155 participants (clade C [n = 26], bivalent protein [n = 103], placebo [n = 26]) received ≥1 injection. The highest adverse event (AE) severity was grade 3 (local pain/tenderness: 12%, 2%, and 0% of the respective groups; solicited systemic AEs: 19%, 15%, 0%). HIV-1 mosaic gp140-binding antibody titers were 79,595 ELISA units [EU]/mL and 137,520 EU/mL in the clade C and bivalent protein groups (P < .001) post-dose 4 and 16,862 EU/mL and 25,162 EU/mL 6 months later. Antibody response breadth against clade C gp140 and clade C/non-clade C gp120 was highest in the bivalent protein group.Conclusions: Adding mosaic gp140 to the clade C regimen increased and broadened the elicited immune response without compromising safety or clade C responses. [ABSTRACT FROM AUTHOR]

Background: The introduction of vaccines during the COVID-19 pandemic provided an opportunity to slow transmission of SARS-CoV-2, but initial uptake of COVID-19 vaccination was slow. We analyzed data from a randomized clinical trial of the mRNA-1273 vaccine (NCT04811664) to describe the patterns of uptake of COVID-19 vaccines among young adults. Methods: The CoVPN 3006 trial randomized adults ages 18–29 from 44 sites in the United States to receive 1) immediate mRNA-1273 vaccination from the study site, or 2) standard of care, including the option to seek vaccination at any time in the future. Randomization occurred between March and November 2021, and an observational arm of adults who declined vaccination was enrolled beginning June 2021. Among participants in the standard of care (SoC) or Vaccine Declined arms, we estimated demographic, behavioral, and health history correlates of vaccination, and the four-month cumulative incidence of COVID-19 vaccination using inverse probability weighted Kaplan-Meier estimators. Results: Among 728 SoC and 470 Vaccine Declined participants, 79% and 16% received COVID-19 vaccination, respectively. SoC and Vaccine Declined participants were more likely to seek and receive vaccination if they reported COVID-19 preventive behaviors, including wearing masks, physically distancing, and avoiding large gatherings. We identified strong predictors of vaccination in the Vaccine Declined arm, including attending class in person (adjusted risk ratio [aRR]: 0.47, 95% confidence interval [CI] 0.21, 1.03), having a COVID-19 relevant medical condition (aRR: 1.95, 95% CI: 0.89, 4.26), and avoiding large gatherings (aRR: 2.24, 95% CI: 1.18, 4.25), though low vaccination rates in this arm led to imprecise estimates. Conclusions: Individuals who initially decline vaccination can be convinced to vaccinate, particularly if they are already practicing other forms of COVID-19 prevention. Continued outreach and education from the scientific community can combat low vaccine confidence. [ABSTRACT FROM AUTHOR]

• Those assigned female at birth experience more reactogenicity. • Most symptoms are mild. • Pain and/or tenderness symptom common in both vaccine and placebo groups. Reactogenicity informs vaccine safety, and may influence vaccine uptake. We evaluated factors associated with reactogenicity in HVTN 702, a typical HIV vaccine efficacy trial with multiple doses and products. HVTN 702, a phase 2b/3 double-blind placebo-controlled trial, randomized 5404 African participants aged 18–35 years without HIV to placebo, or ALVAC-HIV (vCP2438) at months 0, 1 and ALVAC-HIV (vCP2438) + Bivalent Subtype C gp120/MF59 at months 3, 6, 12 and 18. Using multivariate logistic regression, we evaluated associations between reactogenicity with clinical, sociodemographic and laboratory variables. More vaccine than placebo-recipients reported local symptoms (all p < 0.001), arthralgia (p = 0.008), chills (p = 0.012) and myalgia (p < 0.001). Reactogenicity was associated with female sex at birth (OR v = 2.50, OR p = 1.81, both p < 0.001) and geographic region. Amongst vaccine-recipients, each year of age was associated with 3 % increase in reactogenicity (OR = 1.03, p = 0.002). Vaccine receipt, female sex at birth, older age, and region may affect reactogenicity. [ABSTRACT FROM AUTHOR]

Coronavirus disease 2019 (COVID-19) vaccines have yielded definitive prevention and major reductions in morbidity and mortality from severe acute respiratory syndrome coronavirus 2 infection, even in the context of emerging and persistent variants of concern. Newer variants have revealed less vaccine protection against infection and attenuation of vaccine effects on transmission. COVID-19 vaccines still likely reduce transmission compared with not being vaccinated at all, even with variants of concern; however, determining the magnitude of transmission reduction is constrained by the challenges of performing these studies, requiring accurate linkage of infections to vaccine status and timing thereof, particularly within households. In this review, we synthesize the currently available data on the impact of COVID-19 vaccines on infection, serious illness, and transmission; we also identify the challenges and opportunities associated with policy development based on this data. [ABSTRACT FROM AUTHOR]

Background. The safety and immunogenicity of the MRK adenovirus type 5 human immunodeficiency virus type 1 clade B gag/pol/nef vaccine, a replication-incompetent adenovirus type 5-vectored vaccine designed to elicit cell-mediated immunity against conserved human immunodeficiency virus proteins, was assessed in a phase 1 trial. Methods. Healthy adults not infected with human immunodeficiency virus were enrolled in a multicenter, dose-escalating, blind, placebo-controlled study to evaluate a 3-dose homologous prime-boost regimen of the trivalent MRK adenovirus type 5 human immunodeficiency virus type 1 vaccine containing from 3×106 to 1×1011 viral particles per 1-mL dose administered on day 1, during week 4 and during week 26. Adverse events were recorded for 29 days after each intradeltoid injection. The primary immunogenicity end point was the proportion of study participants with a positive unfractionated Gag-, Pol-, or Nef-specific interferon-g enzymelinked immunosorbent spot response measured 4 weeks after administration of the last dose. Results. Of 259 randomized individuals, 257 (99%) received ≥1 dose of vaccine or placebo and were included in the safety analyses. Enzyme-linked immunosorbent spot results were available for 217 study participants (84%) at week 30. No serious vaccine-related adverse events occurred. No study participant discontinued participation because of vaccine-related adverse events. The frequency of injection-site reactions was dose dependent. Vaccine doses of ≥3×109 viral particles elicited positive enzyme-linked immunosorbent spot responses to ≥1 vaccine component in 160% of recipients. High baseline antibody titers against adenovirus type 5 diminished enzymelinked immunosorbent spot responses at all doses except the 3×1010 viral particle dose. Conclusions. The vaccine was generally well tolerated and induced cell-mediated immune responses against human immunodeficiency virus type 1 peptides in most healthy adults. Despite these findings, vaccination in a proof-of-concept trial with use of this vaccine was discontinued because of lack of efficacy. [ABSTRACT FROM AUTHOR]

Mounting evidence has revealed pathological interactions between HIV and malaria in dually infected patients, but the public health implications of the interplay have remained unclear. A transient almost one-log elevation in HIV viral load occurs during febrile malaria episodes; in addition, susceptibility to malaria is enhanced in HIV-infected patients. A mathematical model applied to a setting in Kenya with an adult population of roughly 200,000 estimated that, since 1980, the disease interaction may have been responsible for 8,500 excess HIV infections and 980,000 excess malaria episodes. Co-infection might also have facilitated the geographic expansion of malaria in areas where HIV prevalence is high. Hence, transient and repeated increases in HIV viral load resulting from recurrent co-infection with malaria may be an important factor in promoting the spread of HIV in sub-Saharan Africa. [ABSTRACT FROM AUTHOR]

Background: People infected with Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) experience a wide range of clinical manifestations, from asymptomatic and mild illness to severe illness and death, influenced by age and a variety of comorbidities. Neutralizing antibodies (nAbs) are thought to be a primary immune defense against the virus. Large, diverse, well-characterized cohorts of convalescent individuals provide standardized values to benchmark nAb responses to past SARS-CoV-2 infection and define potentially protective levels of immunity.Methods and Findings: This analysis comprises an observational cohort of 329 HIV-seronegative adults in the United States (n = 167) and Peru (n = 162) convalescing from SARS-CoV-2 infection from May through October 2020. The mean age was 48 years (range 18 to 86), 54% of the cohort overall was Hispanic, and 34% identified as White. nAb titers were measured in serum by SARS-CoV-2.D614G Spike-pseudotyped virus infection of 293T/ACE2 cells. Multiple linear regression was applied to define associations between nAb titers and demographic variables, disease severity and time from infection or disease onset, and comorbidities within and across US and Peruvian cohorts over time. nAb titers peaked 28 to 42 days post-diagnosis and were higher in participants with a history of severe Coronavirus Disease 2019 (COVID-19) (p < 0.001). Diabetes, age >55 years, male sex assigned at birth, and, in some cases, body mass index were also independently associated with higher nAb titers, whereas hypertension was independently associated with lower nAb titers. nAb titers did not differ by race, underlying pulmonary disease or smoking. Two months post-enrollment, nAb ID50 (ID80) titers declined 3.5 (2.8)-fold overall. Study limitations in this observational, convalescent cohort include survivorship bias and missing early viral loads and acute immune responses to correlate with the convalescent responses we observed.Conclusions: In summary, in our cohort, nAb titers after SARS-CoV-2 infection peaked approximately 1 month post-diagnosis and varied by age, sex assigned at birth, disease severity, and underlying comorbidities. Our data show great heterogeneity in nAb responses among people with recent COVID-19, highlighting the challenges of interpreting natural history studies and gauging responses to vaccines and therapeutics among people with recent infection. Our observations illuminate potential correlations of demographic and clinical characteristics with nAb responses, a key element for protection from COVID-19, thus informing development and implementation of preventative and therapeutic strategies globally.Trial Registration: ClinicalTrials.gov NCT04403880. [ABSTRACT FROM AUTHOR]

Supplemental Digital Content is Available in the Text. Background: Measurements of HIV exposure could help identify subpopulations at highest risk of acquisition and improve the design of HIV prevention efficacy trials and public health interventions. The HVTN 915 study evaluated the feasibility of self-administered vaginal swabs for detection of HIV virions to assess exposure. Methods: Fifty 18- to 25-year-old sexually active HIV-seronegative women using contraception were enrolled in Soweto, South Africa. Participants self-administered daily vaginal swabs and answered sexual behavior questions through mobile phone for 90 days. Clinician-administered vaginal swabs, behavioral questionnaires, HIV diagnostic testing, and counseling were performed at 8 clinic visits. Glycogen concentrations assessed adherence to swabbing. Y-chromosome DNA (Yc-DNA) assessed the accuracy of reported condom use. HIV exposure was measured by virion polymerase chain reaction in swabs from 41 women who reported unprotected vaginal sex during follow-up. Results: Glycogen was detected in 315/336 (93.8%) participant-collected and in all clinician-collected swabs. Approximately 20/39 daily swabs (51.3%) linked to mobile reports of unprotected sex tested positive for Yc-DNA, whereas 10/187 swabs collected after 3 days of abstinence or protected sex (5.3%) had detectable Yc-DNA. No participant became HIV infected during the study; yet, exposure to HIV was detected by nucleic acids in 2 vaginal swabs from 1 participant, collected less than 1 hour after coitus. Conclusion: There was high adherence to daily vaginal swabbing. Daily mobile surveys had accurate reporting of unprotected sex. Detection of HIV in self-collected vaginal swabs from an uninfected participant demonstrated it was possible to measure HIV exposure, but the detection rate was lower than expected. [ABSTRACT FROM AUTHOR]

• Nucleic acid testing for pre-ribosomal RNA of M. bovis BCG and M. tuberculosis was optimized. • Method comparison studies on ex vivo mouse tissue samples showed excellent agreement between pre-ribosomal RNA and conventional colony-forming unit culture-based assays. • Molecular viability testing using pre-ribosomal RNA detected viable M. bovis BCG and M. tuberculosis in murine skin and lung tissues. Efforts are underway globally to develop effective vaccines and drugs against M. tuberculosis (Mtb) to reduce the morbidity and mortality of tuberculosis. Improving detection of slow-growing mycobacteria could simplify and accelerate efficacy studies of vaccines and drugs in animal models and human clinical trials. Here, a real-time reverse transcription PCR (RT-PCR) assay was developed to detect pre-ribosomal RNA (pre-rRNA) of Mycobacterium bovis bacille Calmette-Guérin (BCG) and Mtb. This pre-rRNA biomarker is indicative of bacterial viability. In two different mouse models, the presence of pre-rRNA from BCG and Mtb in ex vivo tissues showed excellent agreement with slower culture-based colony-forming unit assays. The addition of a brief nutritional stimulation prior to molecular viability testing further differentiated viable but dormant mycobacteria from dead mycobacteria. This research has set the stage to evaluate pre-rRNA as a BCG and/or Mtb infection biomarker in future drug and vaccine clinical studies. [ABSTRACT FROM AUTHOR]

Background: HLA strongly influences human immunodeficiency virus type 1 (HIV-1) disease progression. A major contributory mechanism is via the particular HLA-presented HIV-1 epitopes that are recognized by CD8(+) T-cells. Different populations vary considerably in the HLA alleles expressed. We investigated the HLA-specific impact of the MRKAd5 HIV-1 Gag/Pol/Nef vaccine in a subset of the infected Phambili cohort in whom the disease-susceptible HLA-B*58:02 is highly prevalent.Methods: Viral loads, CD4(+) T-cell counts, and enzyme-linked immunospot assay-determined anti-HIV-1 CD8(+) T-cell responses for a subset of infected antiretroviral-naive Phambili participants, selected according to sample availability, were analyzed.Results: Among those expressing disease-susceptible HLA-B*58:02, vaccinees had a lower chronic viral set point than placebo recipients (median, 7240 vs 122 500 copies/mL; P = .01), a 0.76 log10 lower longitudinal viremia level (P = .01), and slower progression to a CD4(+) T-cell count of <350 cells/mm(3) (P = .02). These differences were accompanied by a higher Gag-specific breadth (4.5 vs 1 responses; P = .04) and magnitude (2300 vs 70 spot-forming cells/10(6) peripheral blood mononuclear cells; P = .06) in vaccinees versus placebo recipients.Conclusions: In addition to the known enhancement of HIV-1 acquisition resulting from the MRKAd5 HIV-1 vaccine, these findings in a nonrandomized subset of enrollees show an HLA-specific vaccine effect on the time to CD4(+) T-cell count decline and viremia level after infection and the potential for vaccines to differentially alter disease outcome according to population HLA composition.Clinical Trials Registration: NCT00413725, DOH-27-0207-1539. [ABSTRACT FROM AUTHOR]

Background. In 2007, Malawi replaced sulfadoxine-pyrimethamine (SP) with an artemisinin-based combination therapy as the first-line treatment for uncomplicated Plasmodium falciparum malaria in response to failing SP efficacy. Here we estimate the effect of reduced SP pressure on the prevalence of SP-resistant parasites and the characteristics of the associated selective sweeps flanking the resistance loci. Methods. Samples obtained from individuals with clinical malaria during a period of high SP use (1999-2001), a transitional period (2007-2008), and a period of low SP use (2012) were genotyped for resistance markers at pfdhfr-ts codons 51, 59, and 108 and pfdhps codons 437, 540, and 581. Expected heterozygosity was estimated to evaluate the genetic diversity flanking pfdhfr-ts and pfdhps. Results. An increase in the prevalence of the resistance haplotypes DHFR 51I/59R/108N and DHPS 437G/540E occurred under sustained drug pressure, with no change in haplotype prevalence 5 years after reduction in SP pressure. The DHPS 437G/540E/581G haplotype was observed in 2007 and increased in prevalence during a period of reduced SP pressure. Changes to the sweep characteristics flanking pfdhfr-ts and pfdhps were minimal. Conclusions. In contrast to the rapid and complete return of chloroquine-susceptible falciparum malaria after chloroquine was withdrawn from Malawi, a reemergence of SP efficacy is unlikely in the near future. [ABSTRACT FROM AUTHOR]

Plasmid DNA vaccines have been licensed for use in domesticated animals because of their excellent immunogenicity, but none have yet been licensed for use in humans. Here we report a retrospective analysis of 1218 healthy human volunteers enrolled in 10 phase I clinical trials in which DNA plasmids encoding HIV antigens were administered. Elicited T-cell immune responses were quantified by validated intracellular cytokine staining (ICS) stimulated with HIV peptide pools. HIV-specific binding and neutralizing antibody activities were also analyzed using validated assays. Results showed that, in the absence of adjuvants and boosting with alternative vaccines, DNA vaccines elicited CD8+ and CD4+ T-cell responses in an average of 13.3% (95% CI: 9.8–17.8%) and 37.7% (95% CI: 31.9–43.8%) of vaccine recipients, respectively. Three vaccinations (vs. 2) improved the proportion of subjects with antigen-specific CD8+ responses ( p = 0.02), as did increased DNA dosage ( p = 0.007). Furthermore, female gender and participants having a lower body mass index were independently associated with higher CD4+ T-cell response rate ( p = 0.001 and p = 0.008, respectively). These vaccines elicited minimal neutralizing and binding antibody responses. These findings of the immunogenicity of HIV DNA vaccines in humans can provide guidance for future clinical trials. [ABSTRACT FROM AUTHOR]

Objectives. We developed and evaluated a novel National Institutes of Health-sponsored Research and Mentorship Program for African American and Hispanic medical students embedded within the international, multisite HIV Vaccine Trials Network, and explored its impact on scientific knowledge, acquired skills, and future career plans. Methods. Scholars conducted social, behavioral, clinical, or laboratory-based research projects with HIV Vaccine Trials Network investigators over 8 to 16 weeks (track 1) or 9 to 12 months (track 2). We conducted an in-depth, mixed-methods evaluation of the first 2 cohorts (2011-2013) to identify program strengths, areas for improvement, and influence on professional development. Results. A pre-post program assessment demonstrated increases in self-reported knowledge, professional skills, and interest in future HIV vaccine research. During in-depth interviews, scholars reported that a supportive, centrally administered program; available funding; and highly involved mentors and staff were keys to the program's early success. Conclusions. A multicomponent, mentored research experience that engages medical students from underrepresented communities and is organized within a clinical trials network may expand the pool of diverse public health scientists. Efforts to sustain scholar interest over time and track career trajectories are warranted. [ABSTRACT FROM AUTHOR]

Background. Coinfection with human immunodeficiency virus (HIV) may increase susceptibility to malaria by compromising naturally acquired immunity.Methods. In 339 adults (64% HIV infected), we measured antibodies to Plasmodium falciparum variant surface antigens (VSA) and antibodies that opsonise infected erythrocytes using parasite lines FCR3, E8B, and R29, and antibodies to merozoite antigens AMA-1 and MSP2. We determined the relationship between malaria antibodies, HIV infection, markers of immune compromise, and risk of incident parasitemia.Results. HIV-infected adults had significantly lower mean levels of opsonizing antibody to all parasite lines (P < .0001), and lower levels of antibody to AMA-1 (P = .01) and MSP2 (P < .0001). Levels of immunoglobulin G (IgG) to VSA were not affected by HIV status. Opsonising antibody titres against some isolates were positively correlated with CD4 count. There were negative associations between human immunodeficiency virus type 1 (HIV-1) viral load and opsonizing antibodies to FCR3 (P = .04), and levels of IgG to AMA-1 (P ≤ .03) and MSP2-3D7 (P = .05). Lower opsonizing antibody levels on enrollment were seen in those who became parasitemic during follow-up, independent of HIV infection (P ≤ .04 for each line).Conclusions. HIV-1 infection decreases opsonizing antibodies to VSA, and antibody to merozoite antigens. Opsonizing antibodies were associated with lack of parasitemia during follow up, suggesting a role in protection. [ABSTRACT FROM AUTHOR]

Summary: Background: The HVTN 503/Phambili study, which assessed the efficacy of the Merck Ad5 gag/pol/nef subtype B HIV-1 preventive vaccine in South Africa, was stopped when futility criteria in the Step study (assessing the same vaccine in the Americas, Caribbean, and Australia) were met. Here we report long-term follow-up data. Methods: HVTN 503/Phambili was a double-blind, placebo-controlled, randomised trial that recruited HIV-1 uninfected, sexually active adults aged 18–35 years from five sites in South Africa. Eligible participants were randomly assigned (1:1) by computer-generated random numbers to either vaccine or placebo, stratified by site and sex. Cox proportional hazards models were used to estimate HIV-1 infection in the modified intention-to-treat cohort, all of whom were unmasked early in follow-up. The trial is registered with ClinicalTrials.gov, number NCT00413725 and the South African National Health Research Database, number DOH-27-0207-1539. Findings: Between Jan 24, 2007, and Sept 19, 2007, 801 participants (26·7%) of a planned 3000 were randomly assigned (400 to vaccine, 401 to placebo); 216 (27%) received only one injection, 529 (66%) received only two injections, and 56 (7%) received three injections. At a median follow-up of 42 months (IQR 31–42), 63 vaccine recipients (16%) had HIV-1 infection compared with 37 placebo recipients (9%; adjusted HR 1·70, 95% CI 1·13–2·55; p=0·01). Risk for HIV-1 infection did not differ according to the number of vaccinations received, sex, circumcision, or adenovirus type 5 (Ad5) serostatus. Differences in risk behaviour at baseline or during the study, or annualised dropout rate (7·7% [95% CI 6·2–9·5] for vaccine recipients vs 8·8% [7·1–10·7] for placebo recipients; p=0·40) are unlikely explanations for the increased rate of HIV-1 infections seen in vaccine recipients. Interpretation: The increased risk of HIV-1 acquisition in vaccine recipients, irrespective of number of doses received, warrants further investigation to understand the biological mechanism. We caution against further use of the Ad5 vector for HIV vaccines. Funding: National Institute of Allergy and Infectious Diseases, Merck, and South African Medical Research Council. [ABSTRACT FROM AUTHOR]

A response by Laith J. Abu-Raddad, Padmaja Patnaik and James G. Kublin is presented to a letter to the editor about their article "Dual infection with HIV and malaria fuels the spread of both diseases in sub-Saharan Africa," published in the December 8, 2006 issue of the journal.

Background. We report composite results from the Merck phase I program of near-consensus clade B human immunodeficiency virus (HIV) type 1 gag vaccines. Methods. Healthy HIV-uninfected adults were enrolled in 6 blinded placebo-controlled studies evaluating the immunogenicity of (1) a 4-dose regimen of a DNA vaccine, (2) a 3-dose priming regimen of the DNA vaccine with a booster dose of an adenovirus type 5 (Ad5)-vectored vaccine, or (3) a 3-dose regimen of the Ad5 vaccine. The DNA plasmid was provided with or without an aluminum phosphate or CRL1005 adjuvant. The primary end point was the unfractionated HIV-1 gag-specific interferon γ enzyme-linked immunospot (ELISpot) response 4 weeks after the final dose. Results. Overall, 254 (83%) of 307 subjects randomized to the vaccine groups were evaluable. Adjuvants did not enhance immunogenicity of the DNA vaccine. Postboost ELISpot responder frequencies were higher for Ad5-containing regimens than for the DNA/DNA regimen (33%) but were similar for DNA/Ad5 (55%) and Ad5/Ad5 (50%). DNA/DNA elicited mainly a CD4 response, whereas Ad5/Ad5 elicited mainly a CD8 response; DNA/Ad5 generated CD4 and CD8 responses comparable to those of DNA/DNA and Ad5/Ad5, respectively. Conclusions. The DNA vaccine alone or as a priming regimen for the Ad5 vaccine did not increase unfractionated ELISpot responses compared with the Ad5 vaccine alone. Qualitative T cell responses to different vaccine regimens deserve further study. [ABSTRACT FROM AUTHOR]

Background. The genetic diversity of human immunodeficiency virus type 1 (HIV- 1) raises the question of whether vaccines that include a component to elicit antiviral T cell immunity based on a single viral genetic clade could provide cellular immune protection against divergent HIV-1 clades. Therefore, we quantified the cross-clade reactivity, among unvaccinated individuals, of anti-HIV- 1 T cell responses to the infecting HIV- 1 clade relative to other major circulating clades. Methods. Cellular immune responses to HIV- 1 clades A, B, and C were compared by standardized interferon- y enzyme-linked immunospot assays among 250 unvaccinated individuals, infected with diverse HIV- 1 clades, from Brazil, Malawi, South Africa, Thailand, and the United States. Cross-clade reactivity was evaluated by use of the ratio of responses to heterologous versus homologous (infecting) clades of HIV- 1. Results. Cellular immune responses were predominantly focused on viral Gag and Nef proteins. Cross-clade reactivity of cellular immune responses to HIV- 1 clade A, B, and C proteins was substantial for Nef proteins (ratio, 0.97 [95% confidence interval, 0.89-1.05]) and lower for Gag proteins (ratio, 0.67 [95% confidence interval, 0.62- 0.73]). The difference in cross-clade reactivity to Nef and Gag proteins was significant (P < .0001). Conclusions. Cross-clade reactivity of cellular immune responses can be substantial but varies by viral protein. [ABSTRACT FROM AUTHOR]

In eastern and southern Africa, there has been a rapid increase in the prevalence of alleles with mutations in the Plasmodium falciparum dihydrofolate reductase gene (dhfr) associated with increased risk of clinical failure of sulfadoxine-pyrimethamine (S/P). Molecular methods for surveillance of these mutations are now widespread, but the usual analysis detects only the most prevalent allele in a polyclonal sample. We used a yeastexpression system to identify rare, highly pyrimethamine-resistant alleles of dhfr in isolates from 5 African countries-Kenya, Tanzania, Malawi, Gabon, and Nigeria. Only the isolates from Nigeria yielded significant numbers of novel resistant alleles, and only 1 of the alleles from any location showed a >3-fold increase in resistance to S/P or to chlorproguanil-dapsone. Overall, these results suggest that dhfr alleles that confer high levels of resistance to antifolates are rare, even in eastern and southern Africa, where pyrimethamine has been intensively used. [ABSTRACT FROM AUTHOR]

Background: CD4+ T cells expressing α4β7 are optimal targets for HIV infections, with higher pre-HIV α4β7hi expression linked to increased HIV acquisition and progression in South African women. However, similar associations were not observed in men who have sex with men (MSM) or people who inject drugs (PWID) in the Americas, indicating need for further research., Methods: This retrospective case-control study enrolled heterosexual men and women from South Africa (HIV Vaccine Trials Network; HVTN 503) and East Africa (Partners Pre-Exposure Prophylaxis/Couples' Observational Study; PP/COS), quantifying α4β7 expression on CD4+ T cells as a predictor of subsequent HIV risk using flow cytometry analyses., Results: Associations between α4β7hi expression and HIV acquisition varied across cohorts. In HVTN 503, women had a higher risk estimate compared to men, but this was not significant. In PP/COS, α4β7hi expression was generally protective, particularly in Ugandans. Additionally, α4β7hi expression inversely correlated with peak viral load in PP/COS but not in HVTN 503; in the latter cohort, α4β7hi expression was inversely correlated with the CD4/CD8 ratio and predicted rapid CD4+ T cell decline, similar to what was observed previously in South Africa., Conclusions: These findings suggest that α4β7hi expression on CD4+ T cells may not predict HIV acquisition and progression in all contexts, which may be due to cohort effects, modes of transmission, viral clade, or other factors., (© The Author(s) 2024. Published by Oxford University Press on behalf of Infectious Diseases Society of America.)

Utilizing transiently transfected cell lines could significantly reduce manufacturing timelines for protein subunit vaccines. This trial compared safety and immunogenicity of human immunodeficiency virus (HIV) envelope CH505TF gp120 vaccines produced by upstream stable and transient transfection (each admixed with GLA-SE adjuvant, a TL4 agonist). Both vaccines were safe and well tolerated. Serum IgG binding antibody response rates 2 weeks after final injection were 92% in the stable group and 93% in the transient group (P = 1.000). Neutralization response rates against CH505.w4.3 were also equivalent (92% vs 100%, P = .291). These data support transient transfection as an available tool for accelerating HIV vaccine testing and iteration. Clinical Trials Registration. NCT03856996., Competing Interests: Potential conflicts of interest. All authors: No reported conflicts. All authors have submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest. Conflicts that the editors consider relevant to the content of the manuscript have been disclosed., (© The Author(s) 2024. Published by Oxford University Press on behalf of Infectious Diseases Society of America. All rights reserved. For commercial re-use, please contact reprints@oup.com for reprints and translation rights for reprints. All other permissions can be obtained through our RightsLink service via the Permissions link on the article page on our site—for further information please contact journals.permissions@oup.com.)

Background: HIV type 1 (HIV-1) remains a global health concern, with the greatest burden in sub-Saharan Africa. Despite 40 years of research, no vaccine candidate has shown durable and protective efficacy against HIV-1 acquisition. Although pre-exposure prophylaxis in groups with high vulnerability can be very effective, barriers to its use, such as perceived low acquisition risk, fear of stigma, and concerns about side-effects, remain. Thus, a population-based approach, such as an HIV-1 vaccine, is needed. The current study aimed to evaluate the efficacy and safety of a heterologous HIV-1 vaccine regimen, consisting of a tetravalent mosaic adenovirus 26-based vaccine (Ad26.Mos4.HIV) and aluminium phosphate-adjuvanted clade C glycoprotein (gp) 140, in young women at risk of acquiring HIV-1 in southern Africa., Methods: This randomised, double-blind, phase 2b study enrolled sexually active women without HIV-1 or HIV-2 aged 18-35 years at 23 clinical research sites in Malawi, Mozambique, South Africa, Zambia, and Zimbabwe. Participants were centrally randomly assigned (1:1) to receive intramuscular injections of vaccine or saline placebo in stratified permuted blocks via an interactive web response system. Study participants, study site personnel (except those with primary responsibility for study vaccine preparation and dispensing), and investigators were masked to treatment group allocation. The vaccine regimen consisted of Ad26.Mos4.HIV administered at months 0 and 3 followed by Ad26.Mos4.HIV administered concurrently with aluminium phosphate-adjuvanted clade C gp140 at months 6 and 12. The primary efficacy outcome was vaccine efficacy in preventing laboratory-confirmed HIV-1 acquisition diagnosed between visits at month 7 and month 24 after the first vaccination (VE[7-24]) in the per-protocol population, which included participants who had not acquired HIV-1 4 weeks after the third vaccination, received all planned vaccinations at the first three vaccination visits within the protocol-specified windows, and had no major protocol deviations that could affect vaccine efficacy. Primary safety outcomes were assessed in randomly assigned participants who received one study injection or more based on the actual injection received. The primary safety endpoints were the incidences of unsolicited adverse events (AEs), solicited local and systemic AEs, serious AEs, AEs of special interest, and AEs leading to discontinuation of vaccination. This trial is registered with ClinicalTrials.gov, NCT03060629, and is complete., Findings: Between Nov 3, 2017, and June 30, 2019, 2654 women were randomly assigned, of whom 2636 women (median age of 23 years [IQR 20-25]) were enrolled and received at least one study injection (1313 assigned vaccine, 1323 placebo; 1317 received vaccine, 1319 placebo). Analysis of the primary efficacy outcome in the per-protocol cohort included 1080 women in the vaccine group and 1108 women in the placebo group; the incidence of HIV-1 acquisition per 100 person-years over months 7-24 after the first vaccination was 3·38 (95% CI 2·54-4·41) in the vaccine group and 3·94 (3·04-5·03) in the placebo group, with an estimated VE(7-24) of 14·10% (95% CI -22·00 to 39·51; p=0·40). There were no serious unsolicited AEs, AEs of special interest, or deaths related to the study vaccine. In the vaccine group, 663 (50·3%) of 1317 participants had grade 1 or 2 solicited local AEs and ten (0·8%) of 1317 participants had grade 3 or 4 solicited local AEs. In the placebo group, 305 (23·1%) of 1319 participants had grade 1 or 2 solicited local AEs and three (0·2%) of 1319 participants had grade 3 or 4 solicited local AEs. 863 (65·5%) of 1317 participants in the vaccine group had grade 1 or 2 solicited systemic AEs and 34 (2·6%) of 1317 participants had grade 3 or 4 solicited systemic AEs. 763 (57·8%) of 1319 participants in the placebo group had grade 1 or 2 solicited systemic AEs and 20 (1·5%) of 1319 participants had grade 3 or 4 solicited systemic AEs. Overall, three (0·2%) of 1317 participants in the vaccine group and three (0·2%) of 1319 participants in the placebo group discontinued vaccination due to an unsolicited AE, and three (0·2%) of 1317 participants in the vaccine group and one (0·1%) of 1319 participants in the placebo group discontinued vaccination due to a solicited AE., Interpretation: The heterologous Ad26.Mos4.HIV and clade C gp140 vaccine regimen was safe and well tolerated but did not show efficacy in preventing HIV-1 acquisition in a population of young women in southern Africa at risk of HIV-1., Funding: Division of AIDS at the National Institute of Allergy and Infectious Diseases through the HIV Vaccine Trials Network, Bill & Melinda Gates Foundation, Janssen Vaccines & Prevention, US Army Medical Materiel Development Activity, and Ragon Institute., Competing Interests: Declaration of interests GEG's institution (the South African Medical Research Council) has received funding from the US National Institutes of Health (NIH) and the Bill & Melinda Gates Foundation. KM was a protocol co-chair for the Imbokodo trial. LL is a consultant for Janssen Infectious Diseases. SN, DJS, JvD, WW, JVH, HS, MGP, and FT were employees of Janssen Pharmaceuticals at the time of this study and are stockholders of Johnson & Johnson. AL's institution has received funding from the NIH; outside the submitted work, AL has received consulting fees from Harvard University, and his institution has received funding from Janssen Pharmaceuticals. PM is an employee and stockholder of CureVac. MJM's institution (Fred Hutchinson Cancer Center) has received funding, including for laboratory equipment purchases, from the HIV Vaccine Trials Network (HVTN) Laboratory Center (grant number 5UM1AI068618) and Seattle-Lausanne Clinical Trials Unit; outside the submitted work, her institution has received funding, including for laboratory equipment purchases, from the Scripps Consortium for HIV/AIDS Vaccine Development Subaward, National Institute of Allergy and Infectious Diseases (NIAID) Human Immunology Project Consortium 3, Bill & Melinda Gates Foundation Comprehensive Cellular Vaccine Immune Monitoring Consortium, and Bill & Melinda Gates Foundation Collaboration for AIDS Vaccine Discovery; her institution has received funding, including for laboratory equipment purchases, supporting SARS-CoV-2 vaccine laboratory studies from the COVID-19 Prevention Network (NIAID), Janssen Pharmaceuticals, Infectious Diseases Clinical Research Consortium (NIAID), Sanofi Pasteur, Moderna, and Regeneron; her institution has received funding, including for laboratory equipment purchases, supporting HIV and other vaccine trials and laboratory studies from International AIDS Vaccine Initiative, Janssen Pharmaceuticals, and Vir Biotechnology; and she has participated in scientific advisory boards for the Ragon Institute and Keystone Symposia, and on a board of scientific counsellors for the NIH Vaccine Research Center. GDT's institution (Duke University) has received NIH funding through the HVTN (grant numbers 5UM1AI068614 and 5UM1AI068618); GDT has served as a consultant for and received funding to her institution through Janssen Pharmaceuticals; is a reviewer for the Gilead Research Scholar Program; and has served on the board of scientific counsellors for the NIH Vaccine Research Center. DHB is a co-inventor on HIV vaccine patents that have been licensed to Janssen Pharmaceuticals. SB has received grant funding from Gilead Sciences, Merck, GSK, and ViiV. All other authors declare no competing interests., (Copyright © 2024 The Author(s). Published by Elsevier Ltd. This is an Open Access article under the CC BY 4.0 license. Published by Elsevier Ltd.. All rights reserved.)

Background: The neonatal immune system is uniquely poised to generate broadly neutralizing antibodies (bnAbs) and thus infants are ideal for evaluating HIV vaccine candidates. We present the design and safety of a novel glucopyranosyl lipid A (GLA)-stable emulsion (SE) adjuvant admixed with a first-in-infant CH505 transmitter-founder (CH505TF) gp120 immunogen designed to induce precursors for bnAbs against HIV., Methods: HVTN 135 is a phase I randomized, placebo-controlled trial of CH505TF+GLA-SE or placebo. Healthy infants in South Africa aged ≤5 days, born to mothers living with HIV but HIV nucleic acid negative at birth were randomized to five doses of CH505TF + GLA-SE or placebo at birth and 8, 16, 32, and 54 weeks., Results: 38 infants (median age = 4 days; interquartile range 4, 4.75 days) were enrolled November 2020 to January 2022. Among 28 (10) infants assigned to receive CH505TF + GLA-SE (placebo), most (32/38) completed the 5-dose immunization series and follow-up (35/38). Solicited local and systemic reactions were more frequent in vaccine (8, 28.6% local; 16, 57.1% systemic) vs. placebo recipients (1, 10% local, p = 0.25; 4, 40.0% systemic, p = 0.38). All events were Grade 1 except two Grade 2 events (pain, lethargy). Serious vaccine-related adverse events were not recorded., Conclusions: This study illustrates the feasibility of conducting trials of novel adjuvanted HIV vaccines in HIV-exposed infants receiving standard infant vaccinations. The safety profile of the CH505TF + GLA-SE vaccine was reassuring., Trial Registration: ClinicalTrials.gov NCT04607408., Funding: National Institute of Allergy and Infectious Diseases (NIAID) at the National Institutes of Health (NIH)., Competing Interests: Declaration of interests OL is a named inventor on patents relating to vaccine adjuvants and to human in vitro systems that model the safety and immunogenicity of adjuvants, vaccines and immunomodulators. He serves as a consultant to GSK and Hillevax and is a co-founder of Ovax, Inc. All other authors declare no conflict of interest.

Background: The HVTN 705 Imbokodo trial of 2636 people without HIV and assigned female sex at birth, conducted in southern Africa, evaluated a heterologous HIV-1 vaccine regimen: mosaic adenovirus 26-based vaccine (Ad26.Mos4.HIV) at Months 0, 3, 6, 12 and alum-adjuvanted clade C gp140 at Months 6, 12. Per-protocol vaccine efficacy (VE) against HIV-1 diagnosis from seven to 24 months was 14.1% (95% CI: -22.0% to 39.5%). Immune correlates analysis was performed for markers selected based on prior evidence in efficacy trials and/or nonhuman primate models., Methods: Humoral and cellular immune response markers at Month 7 were evaluated as immune correlates of risk and of protection in a breakthrough case-control cohort (n = 52 cases, 246 non-cases). Primary markers were IgG binding to vaccine-strain gp140, IgG3 binding to diverse Env antigens (IgG3 Env breadth), IgG3 binding to diverse V1V2 antigens (IgG3 V1V2 breadth), antibody-dependent phagocytosis against the vaccine-strain gp140, Env-specific CD4+ and CD8+ T-cell responses, and multi-epitope functions., Findings: No immune markers were statistically significant correlates of risk. IgG3 V1V2 breadth trended toward an inverse association: hazard ratio 0.70 (95% CI: 0.36 to 1.35; p = 0.29) per 10-fold increase and 0.51 (95% CI: 0.21 to 1.24; p = 0.14) in a Cox model with all primary markers. The VE estimate was 11.8% (95% CI: -17.9% to 34.0%) at all IgG3 V1V2 breadth values below 667 weighted geometric mean net MFI; just above this value, the VE estimate sharply increased to 62.6% (95% CI: -17.9% to 89.6%), and further increased to 80.9% (95% CI: -17.9% to 99.5%) at 1471 MFI, the 95th percentile of the marker distribution. Mediation analysis yielded a VE of 35.7% (95% CI: 15.0% to 51.3%) attributable to the vaccine's impact on this marker., Interpretation: The trend in association of greater IgG3 V1V2 antibody breadth with lower likelihood of HIV acquisition is consistent with the identification of antibodies against V1V2 as immune correlates in three other HIV vaccine efficacy trials and suggests that a greater emphasis should be placed on studying this region in the HIV-1 envelope as a vaccine immunogen., Funding: National Institute of Allergy and Infectious Diseases and Janssen Vaccines & Prevention BV., Competing Interests: Declaration of interests TvdK has a patent application with Johnson & Johnson and has stocks in Johnson & Johnson. BK received internal support for the present manuscript from her employer (Los Alamos National Laboratory). In the past 36 months, she received support for attending meetings and/or travel from NIH NIAID and from the Gates foundation. Her institution (LANL) had a patent on this work, although she did not receive any personal funds through this patent and was not involved with the licensing of the design to Johnson & Johnson. DHB has a patent on the mosaic HIV vaccine, but no royalties. FT was an employee of Janssen/Johnson & Johnson at the time the work was conducted and owns stock in Johnson & Johnson. LL received support from Janssen Infectious Diseases BV, Beerse, Belgium for travel expenses to attend HIV conferences and has stock or stock options in Johnson & Johnson. JvD, MGP, WW, TvdK and JHen are employees of Janssen/Johnson & Johnson and hold stock or stock options in Johnson & Johnson. WW has a patent planned, issued, or pending with Johnson & Johnson. SCDR had contracts in the past 36 months to perform immunogenicity testing for Janssen, Sanofi, and Moderna. HS and DJS were employees of Janssen Vaccines & Prevention BV and had stock and/or stock options in Johnson & Johnson at the time the work was conducted. SN was an employee of Janssen Infectious Diseases BV and had stock and/or stock options in Johnson & Johnson at the time the work was conducted. LP was an employee of Janssen Vaccines & Prevention BV at the time the work was conducted. GDT has received consulting fees for a scientific consulting session. All other authors have no potential competing interests to disclose. Funding for the Imbokodo Study and Correlates Group is the same as listed in “Acknowledgments” for the current work., (Copyright © 2024 The Author(s). Published by Elsevier B.V. All rights reserved.)

In the phase 3 Coronavirus Efficacy (COVE) trial (NCT04470427), post-dose two Ancestral Spike-specific binding (bAb) and neutralizing (nAb) antibodies were shown to be correlates of risk (CoR) and of protection against Ancestral-lineage COVID-19 in SARS-CoV-2 naive participants. In the SARS-CoV-2 Omicron era, Omicron subvariants with varying degrees of immune escape now dominate, seropositivity rates are high, and booster doses are administered, raising questions on whether and how these developments affect the bAb and nAb correlates. To address these questions, we assess post-boost BA.1 Spike-specific bAbs and nAbs as CoRs and as correlates of booster efficacy in COVE. For naive individuals, bAbs and nAbs inversely correlate with Omicron COVID-19: hazard ratios (HR) per 10-fold marker increase (95% confidence interval) are 0.16 (0.03, 0.79) and 0.31 (0.10, 0.96), respectively. In non-naive individuals the analogous results are similar: 0.15 (0.04, 0.63) and 0.28 (0.07, 1.08). For naive individuals, three vs two-dose booster efficacy correlates with predicted nAb titer at exposure, with estimates -8% (-126%, 48%), 50% (25%, 67%), and 74% (49%, 87%), at 56, 251, and 891 Arbitrary Units/ml. These results support the continued use of antibody as a surrogate endpoint., (© 2024. This is a U.S. Government work and not under copyright protection in the US; foreign copyright protection may apply.)

Cutaneous mycobacterial infections cause substantial morbidity and are challenging to diagnose and treat. An improved understanding of the dermal immune response to mycobacteria may inspire new therapeutic approaches. We conducted a controlled human infection study with 10 participants who received 2 × 106 CFUs of Mycobacterium bovis bacillus Calmette-Guérin (Tice strain) intradermally and were randomized to receive isoniazid or no treatment. Peripheral blood was collected at multiple time points for flow cytometry, bulk RNA sequencing (RNA-seq), and serum Ab assessments. Systemic immune responses were detected as early as 8 d postchallenge in this M. bovis bacillus Calmette-Guérin-naive population. Injection-site skin biopsies were performed at days 3 and 15 postchallenge and underwent immune profiling using mass cytometry and single-cell RNA-seq, as well as quantitative assessments of bacterial viability and burden. Molecular viability testing and standard culture results correlated well, although no differences were observed between treatment arms. Single-cell RNA-seq revealed various immune and nonimmune cell types in the skin, and communication between them was inferred by ligand-receptor gene expression. Day 3 communication was predominantly directed toward monocytes from keratinocyte, muscle, epithelial, and endothelial cells, largely via the migration inhibitory factor pathway and HLA-E-KLRK1 interaction. At day 15, communication was more balanced between cell types. These data reveal the potential role of nonimmune cells in the dermal immune response to mycobacteria and the utility of human challenge studies to augment our understanding of mycobacterial infections., (Copyright © 2024 The Authors.)

Background: HVTN 120 is a phase 1/2a randomized double-blind placebo-controlled human immunodeficiency virus (HIV) vaccine trial that evaluated the safety and immunogenicity of ALVAC-HIV (vCP2438) and MF59- or AS01B-adjuvanted bivalent subtype C gp120 Env protein at 2 dose levels in healthy HIV-uninfected adults., Methods: Participants received ALVAC-HIV (vCP2438) alone or placebo at months 0 and 1. At months 3 and 6, participants received either placebo, ALVAC-HIV (vCP2438) with 200 μg of bivalent subtype C gp120 adjuvanted with MF59 or AS01B, or ALVAC-HIV (vCP2438) with 40 μg of bivalent subtype C gp120 adjuvanted with AS01B. Primary outcomes were safety and immune responses., Results: We enrolled 160 participants, 55% women, 18-40 years old (median age 24 years) of whom 150 received vaccine and 10 placebo. Vaccines were generally safe and well tolerated. At months 6.5 and 12, CD4+ T-cell response rates and magnitudes were higher in the AS01B-adjuvanted groups than in the MF59-adjuvanted group. At month 12, HIV-specific Env-gp120 binding antibody response magnitudes in the 40 μg gp120/AS01B group were higher than in either of the 200 μg gp120 groups., Conclusions: The 40 μg dose gp120/AS01B regimen elicited the highest CD4+ T-cell and binding antibody responses. Clinical Trials Registration . NCT03122223., Competing Interests: Potential conflicts of interest. S. G. is an employee of Sanofi Pasteur and C. A. D. G. was employed by Sanofi Pasteur at the time of the study. M. Ko. and O. V. D. M. are employees of GSK and hold shares in GSK. All other authors report no potential conflicts. Funding to pay the Open Access publication charges for this article was provided by the NIH. All authors have submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest. Conflicts that the editors consider relevant to the content of the manuscript have been disclosed., (© The Author(s) 2023. Published by Oxford University Press on behalf of Infectious Diseases Society of America.)

Background: An effective vaccine is required to end the HIV pandemic. We evaluated the safety and immunogenicity of a DNA (DNA-HIV-PT123) vaccine with low- or high-dose bivalent (TV1.C and 1086.C glycoprotein 120) subtype C envelope protein combinations, adjuvanted with MF59 or AS01B., Methods: HIV Vaccine Trials Network (HVTN)108 was a randomized, placebo-controlled, double-blind, phase 1/2a trial conducted in the United States and South Africa. HIV-negative adults were randomly assigned to 1 of 7 intervention arms or placebo to assess DNA prime with DNA/protein/adjuvant boosts, DNA/protein/adjuvant co-administration, and low-dose protein/adjuvant regimens. HVTN111 trial participants who received an identical regimen were also included. Outcomes included safety and immunogenicity 2 weeks and 6 months after final vaccination., Results: From June 2016 to July 2018, 400 participants were enrolled (N = 334 HVTN108, N = 66 HVTN111); 370 received vaccine and 30 received placebo. There were 48 grade 3 and 3 grade 4 reactogenicity events among 39/400 (9.8%) participants, and 32 mild/moderate-related adverse events in 23/400 (5.8%) participants. All intervention groups demonstrated high IgG response rates (>89%) and high magnitudes to HIV-1 Env gp120 and gp140 proteins; response rates for AS01B-adjuvanted groups approached 100%. V1V2 IgG magnitude, Fc-mediated functions, IgG3 Env response rates, and CD4+ T-cell response magnitudes and rates were higher in the AS01B-adjuvanted groups. The AS01B-adjuvanted low-dose protein elicited greater IgG responses than the higher protein dose., Conclusions: The vaccine regimens were generally well tolerated. Co-administration of DNA with AS01B-adjuvanted bivalent Env gp120 elicited the strongest humoral responses; AS01B-adjuvanted regimens elicited stronger CD4+ T-cell responses, justifying further evaluation.ClinicalTrials.gov registration: NCT02915016, registered 26 September 2016., (Copyright © 2024 The Author(s). Published by Wolters Kluwer Health, Inc.)

A recent clinical trial demonstrated that Bacille Calmette-Guérin (BCG) revaccination of adolescents reduced the risk of sustained infection with Mycobacterium tuberculosis (M.tb). In a companion phase 1b trial, HVTN 602/Aeras A-042, we characterize in-depth the cellular responses to BCG revaccination or to a H4:IC31 vaccine boost to identify T cell subsets that could be responsible for the protection observed. High-dimensional clustering analysis of cells profiled using a 26-color flow cytometric panel show marked increases in five effector memory CD4 + T cell subpopulations (T EM ) after BCG revaccination, two of which are highly polyfunctional. CITE-Seq single-cell analysis shows that the activated subsets include an abundant cluster of Th1 cells with migratory potential. Additionally, a small cluster of Th17 T EM cells induced by BCG revaccination expresses high levels of CD103; these may represent recirculating tissue-resident memory cells that could provide pulmonary immune protection. Together, these results identify unique populations of CD4 + T cells with potential to be immune correlates of protection conferred by BCG revaccination., (© 2024. The Author(s).)

Background: The unprecedented scientific response to the SARS-Cov-2 pandemic in 2020 required the rapid development and activation of extensive clinical trial networks to study vaccines and therapeutics. The COVID-19 Prevention Network (CoVPN) coordinated hundreds of sites conducting phase 2 and 3 clinical trials of vaccines and antibody therapeutics. To facilitate these clinical trials, the CoVPN Volunteer Screening Registry (VSR) was created to collect volunteer information at scale, identify volunteers at risk of COVID-19 who met enrollment criteria, distribute candidates across clinical trial sites, and enable monitoring of volunteering and enrollment progress., Methods: We developed a secure database to support three primary web-based interfaces: a national volunteer questionnaire intake form, a clinical trial site portal, and an Administrative Portal. The Site Portal supported filters based on volunteer attributes, visual analytics, enrollment status tracking, geographic search, and clinical risk prediction. The Administrative Portal supported oversight and development with pre-specified reports aggregated by geography, trial, and trial site; charts of volunteer rates over time; volunteer risk score calculation; and dynamic, user-defined reports., Findings: Over 650,000 volunteers joined the VSR, and 1094 users were trained to utilize the system. The VSR played a key role in recruitment for the Moderna, Oxford-AstraZeneca, Janssen, and Novavax vaccine clinical trials, provided support to the Pfizer and Sanofi vaccine and prophylactic antibody clinical trials, and enhanced the diversity of trial participants. Clinical trial sites selected 166,729 volunteer records for follow-up screening, and of these 47·7% represented groups prioritized for increased enrollment. Despite the unprecedented urgency of its development, the system maintained 99·99% uptime., Interpretation: The success of the VSR demonstrates that information tools can be rapidly yet safely developed through a public-private partnership and integrated into a distributed and accelerated clinical trial setting. We further summarize the requirements, design, and development of the system, and discuss lessons learned for future pandemic preparedness., Competing Interests: Declaration of interests JK, NFA, KM, GBB, MT, and LR declare no conflicts; RL, SS, AK, DM, SM, and JH are employed by Oracle Corporation and hold stock options.

Background: Malaria is a potentially life-threatening disease caused by Plasmodium protozoa transmitted by infected Anopheles mosquitoes. Controlled human malaria infection (CHMI) trials are used to assess the efficacy of interventions for malaria elimination. The operating characteristics of statistical methods for assessing the ability of interventions to protect individuals from malaria is uncertain in small CHMI studies. This paper presents simulation studies comparing the performance of a variety of statistical methods for assessing efficacy of intervention in CHMI trials., Methods: Two types of CHMI designs were investigated: the commonly used single high-dose design (SHD) and the repeated low-dose design (RLD), motivated by simian immunodeficiency virus (SIV) challenge studies. In the context of SHD, the primary efficacy endpoint is typically time to infection. Using a continuous time survival model, five statistical tests for assessing the extent to which an intervention confers partial or full protection under single dose CHMI designs were evaluated. For RLD, the primary efficacy endpoint is typically the binary infection status after a specific number of challenges. A discrete time survival model was used to study the characteristics of RLD versus SHD challenge studies., Results: In a SHD study with the continuous time survival model, log-rank test and t-test are the most powerful and provide more interpretable results than Wilcoxon rank-sum tests and Lachenbruch tests, while the likelihood ratio test is uniformly most powerful but requires knowledge of the underlying probability model. In the discrete time survival model setting, SHDs are more powerful for assessing the efficacy of an intervention to prevent infection than RLDs. However, additional information can be inferred from RLD challenge designs, particularly using a likelihood ratio test., Conclusions: Different statistical methods can be used to analyze controlled human malaria infection (CHMI) experiments, and the choice of method depends on the specific characteristics of the experiment, such as the sample size allocation between the control and intervention groups, and the nature of the intervention. The simulation results provide guidance for the trade off in statistical power when choosing between different statistical methods and study designs., (© 2024. The Author(s).)

Background: An effective HIV vaccine will most likely need to have potent immunogenicity and broad cross-subtype coverage. The aim of the HIV Vaccine Trials Network (HVTN) 124 was to evaluate safety and immunogenicity of a unique polyvalent DNA-protein HIV vaccine with matching envelope (Env) immunogens., Methods: HVTN 124 was a randomised, phase 1, placebo-controlled, double-blind study, including participants who were HIV seronegative and aged 18-50 years at low risk for infection. The DNA vaccine comprised five plasmids: four copies expressing Env gp120 (clades A, B, C, and AE) and one gag p55 (clade C). The protein vaccine included four DNA vaccine-matched GLA-SE-adjuvanted recombinant gp120 proteins. Participants were enrolled across six clinical sites in the USA and were randomly assigned to placebo or one of two vaccine groups (ie, prime-boost or coadministration) in a 5:1 ratio in part A and a 7:1 ratio in part B. Vaccines were delivered via intramuscular needle injection. The primary outcomes were safety and tolerability, assessed via frequency, severity, and attributability of local and systemic reactogenicity and adverse events, laboratory safety measures, and early discontinuations. Part A evaluated safety. Part B evaluated safety and immunogenicity of two regimens: DNA prime (administered at months 0, 1, and 3) with protein boost (months 6 and 8), and DNA-protein coadministration (months 0, 1, 3, 6, and 8). All randomly assigned participants who received at least one dose were included in the safety analysis. The study is registered with ClinicalTrials.gov (NCT03409276) and is closed to new participants., Findings: Between April 19, 2018 and Feb 13, 2019, 60 participants (12 in part A [five men and seven women] and 48 in part B [21 men and 27 women]) were enrolled. All 60 participants received at least one dose, and 14 did not complete follow-up (six of 21 in the prime-boost group and eight of 21 in the coadminstration group). 11 clinical adverse events deemed by investigators as study-related occurred in seven of 48 participants in part B (eight of 21 in the prime-boost group and three of 21 in the coadministration group). Local reactogenicity in the vaccine groups was common, but the frequency and severity of reactogenicity signs or symptoms did not differ between the prime-boost and coadministration groups (eg, 20 [95%] of 21 in the prime-boost group vs 21 [100%] of 21 in the coadministration group had either local pain or tenderness of any severity [p=1·00], and seven [33%] vs nine [43%] had either erythema or induration [p=0·97]), nor did laboratory safety measures. There were no delayed-type hypersensitivity reactions or vasculitis or any severe clinical adverse events related to vaccination. The most frequently reported systemic reactogenicity symptoms in the active vaccine groups were malaise or fatigue (five [50%] of ten in part A and 17 [81%] of 21 in the prime-boost group vs 15 [71%] of 21 in the coadministration group in part B), headache (five [50%] and 18 [86%] vs 12 [57%]), and myalgia (four [40%] and 13 [62%] vs ten [48%]), mostly of mild or moderate severity., Interpretation: Both vaccine regimens were safe, warranting evaluation in larger trials., Funding: US National Institutes of Health and US National Institute of Allergy and Infectious Diseases., Competing Interests: Declaration of interests IF, NG, KES, JRH, SE, SCDR, DEM, DCM, GDT, LC, and SL report support for the present manuscript from National Institutes of Health (NIH), National Institute of Allergy and Infectious Diseases (NIAID), Division of AIDS, and the HIV Vaccine Trials Network (HVTN) paid to their institutions. SCDR and DEM report support for the present manuscript from the Bill & Melinda Gates Foundation, and grants or contracts outside of the submitted work from Janssen, Sanofi, and Moderna. IF reports grants or contracts outside of the submitted work from Janssen, Gilead, Moderna, Pfizer, and Sanofi paid to his institution, consulting fees from Gilead and ViiV, and participation or payment from Janssen for participation on a data safety monitoring board or advisory board. JRH reports support for attending meetings or travel from the HVTN. MCK reports grants or contracts from NIAID outside of the submitted work and participation on a data safety monitoring board or advisory board for the Worcester HIV Vaccine. SL reports royalties or licences from Cosmic Bliss Sciences related to polyvalent DNA–protein HIV vaccine IP from the University of Massachusetts Medical School, Worcester, MA, USA, and reports stock ownership of Cosmic Bliss Sciences since 2023. All other authors declare no competing interests., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Background: Adjuvants are widely used to enhance and/or direct vaccine-induced immune responses yet rarely evaluated head-to-head. Our trial directly compared immune responses elicited by MF59 versus alum adjuvants in the RV144-like HIV vaccine regimen modified for the Southern African region. The RV144 trial of a recombinant canarypox vaccine vector expressing HIV env subtype B (ALVAC-HIV) prime followed by ALVAC-HIV plus a bivalent gp120 protein vaccine boost adjuvanted with alum is the only trial to have shown modest HIV vaccine efficacy. Data generated after RV144 suggested that use of MF59 adjuvant might allow lower protein doses to be used while maintaining robust immune responses. We evaluated safety and immunogenicity of an HIV recombinant canarypox vaccine vector expressing HIV env subtype C (ALVAC-HIV) prime followed by ALVAC-HIV plus a bivalent gp120 protein vaccine boost (gp120) adjuvanted with alum (ALVAC-HIV+gp120/alum) or MF59 (ALVAC-HIV+gp120/MF59) or unadjuvanted (ALVAC-HIV+gp120/no-adjuvant) and a regimen where ALVAC-HIV+gp120 adjuvanted with MF59 was used for the prime and boost (ALVAC-HIV+gp120/MF59 coadministration)., Methods and Findings: Between June 19, 2017 and June 14, 2018, 132 healthy adults without HIV in South Africa, Zimbabwe, and Mozambique were randomized to receive intramuscularly: (1) 2 priming doses of ALVAC-HIV (months 0 and 1) followed by 3 booster doses of ALVAC-HIV+gp120/MF59 (months 3, 6, and 12), n = 36; (2) 2 priming doses of ALVAC-HIV (months 0 and 1) followed by 3 booster doses of ALVAC-HIV+gp120/alum (months 3, 6, and 12), n = 36; (3) 4 doses of ALVAC-HIV+gp120/MF59 coadministered (months 0, 1, 6, and 12), n = 36; or (4) 2 priming doses of ALVAC-HIV (months 0 and 1) followed by 3 booster doses of ALVAC-HIV+gp120/no adjuvant (months 3, 6, and 12), n = 24. Primary outcomes were safety and occurrence and mean fluorescence intensity (MFI) of vaccine-induced gp120-specific IgG and IgA binding antibodies at month 6.5. All vaccinations were safe and well-tolerated; increased alanine aminotransferase was the most frequent related adverse event, occurring in 2 (1.5%) participants (1 severe, 1 mild). At month 6.5, vaccine-specific gp120 IgG binding antibodies were detected in 100% of vaccinees for all 4 vaccine groups. No significant differences were seen in the occurrence and net MFI of vaccine-specific IgA responses between the ALVAC-HIV+gp120/MF59-prime-boost and ALVAC-HIV+gp120/alum-prime-boost groups or between the ALVAC-HIV+gp120/MF59-prime-boost and ALVAC-HIV+gp120/MF59 coadministration groups. Limitations were the relatively small sample size per group and lack of evaluation of higher gp120 doses., Conclusions: Although MF59 was expected to enhance immune responses, alum induced similar responses to MF59, suggesting that the choice between these adjuvants may not be critical for the ALVAC+gp120 regimen., Trial Registration: HVTN 107 was registered with the South African National Clinical Trials Registry (DOH-27-0715-4894) and ClinicalTrials.gov (NCT03284710)., Competing Interests: MK and OVDM are employed by GSK and hold shares in the company. MK reports grants from Bill & Melinda Gates Foundation and grants from NIH during the conduct of the study. NKT was an employee of GSK Biologicals and Novartis Vaccines & Diagnostics during the time of the trial. All other authors have nothing to declare., (Copyright: This is an open access article, free of all copyright, and may be freely reproduced, distributed, transmitted, modified, built upon, or otherwise used by anyone for any lawful purpose. The work is made available under the Creative Commons CC0 public domain dedication.)

Background: Elicitation of broad immune responses is understood to be required for an efficacious preventative HIV vaccine. This Phase 1 randomized controlled trial evaluated whether administration of vaccine antigens separated at multiple injection sites vs combined, fractional delivery at multiple sites affected T-cell breadth compared to standard, single site vaccination., Methods: We randomized 90 participants to receive recombinant adenovirus 5 (rAd5) vector with HIV inserts gag, pol and env via three different strategies. The Standard group received vaccine at a single anatomic site (n = 30) compared to two polytopic (multisite) vaccination groups: Separated (n = 30), where antigens were separately administered to four anatomical sites, and Fractioned (n = 30), where fractions of each vaccine component were combined and administered at four sites. All groups received the same total dose of vaccine., Findings: CD8 T-cell response rates and magnitudes were significantly higher in the Fractioned group than Standard for several antigen pools tested. CD4 T-cell response magnitudes to Pol were higher in the Separated than Standard group. T-cell epitope mapping demonstrated greatest breadth in the Fractioned group (median 8.0 vs 2.5 for Standard, Wilcoxon p = 0.03; not significant after multiplicity adjustment for co-primary endpoints). IgG binding antibody response rates to Env were higher in the Standard and Fractioned groups vs Separated group., Interpretation: This study shows that the number of anatomic sites for which a vaccine is delivered and distribution of its antigenic components influences immune responses in humans., Funding: National Institute of Allergy and Infectious Diseases, NIH., Competing Interests: Declaration of interests MAA is employed by NIAID, the funder of the study. HVT, KJB, SAK, AFG, LC, GDT, NF, NG, SCDR reports receiving institutional grants from the NIH. IF reports institutional grants and participation on Boards of Gilead and Viiv; LB reports institutional grants and participation on Boards of the FDA and NIAID; MJM reports institutional grants, participation on Boards of Ragon Institute, Keystone Symposia and NIH VRC, and a patent on HIV immunogens. The rest of the authors as well as HVTN 085 Study Team declare no conflicts of interest., (Copyright © 2024 The Author(s). Published by Elsevier B.V. All rights reserved.)

Background: The human gut microbiome develops rapidly during infancy, a key window of development coinciding with maturation of the adaptive immune system. However, little is known of the microbiome growth dynamics over the first few months of life and whether there are any generalizable patterns across human populations. We performed metagenomic sequencing on stool samples (n=94) from a cohort of infants (n=15) at monthly intervals in the first six months of life, augmenting our dataset with seven published studies for a total of 4,441 metagenomes from 1,162 infants., Results: Strain-level de novo analysis was used to identify 592 of the most abundant organisms in the infant gut microbiome. Previously unrecognized consortia were identified which exhibited highly correlated abundances across samples and were composed of diverse species spanning multiple genera. Analysis of a cohort of infants with cystic fibrosis identified one such novel consortium of diverse Enterobacterales which was positively correlated with weight gain. While all studies showed an increased community stability during the first year of life, microbial dynamics varied widely in the first few months of life, both by study and by individual., Conclusion: By augmenting published metagenomic datasets with data from a newly established cohort we were able to identify novel groups of organisms that are correlated with measures of robust human development. We hypothesize that the presence of these groups may impact human health in aggregate in ways that individual species may not in isolation., Competing Interests: Competing interests: The authors declare that they have no competing interests.

Nucleic acid vaccines, including both RNA and DNA platforms, are key technologies that have considerable promise in combating both infectious disease and cancer. However, little is known about the extrinsic factors that regulate nucleic acid vaccine responses and which may determine their effectiveness. The microbiome is recognized as a significant regulator of immune development and response, whose role in regulating some traditional vaccine platforms has recently been discovered. Using germ-free and specific pathogen-free mouse models in combination with different protein, DNA, and mRNA vaccine regimens, we demonstrate that the microbiome is a significant regulator of nucleic acid vaccine immunogenicity. Although the presence of the microbiome enhances CD8+ T cell responses to mRNA lipid nanoparticle immunization, the microbiome suppresses Ig and CD4+ T cell responses to DNA-prime, DNA-protein-boost immunization, indicating contrasting roles for the microbiome in the regulation of these different nucleic acid vaccine platforms. In the case of mRNA lipid nanoparticle vaccination, germ-free mice display reduced dendritic cell/macrophage activation that may underlie the deficient vaccine response. Our study identifies the microbiome as a relevant determinant of nucleic acid vaccine response with implications for continued therapeutic development and deployment of these vaccines., (Copyright © 2023 by The American Association of Immunologists, Inc.)

Many promising vaccine candidates and licensed vaccines lead to variable immune responses within humans. Studies suggest that environmental exposures in the gastrointestinal tract could contribute to a reduction in vaccine efficacy via immune tolerance at this site; this is partly achieved by a high abundance of regulatory T cells (Tregs). It is unclear if Treg subsets regulate systemic vaccine responses following oral antigen pre-exposure. Here, we implemented a conditional knock-out mouse model of RORγt+ Tregs to examine the role of these cells in mediating this process. Following oral exposure to the model antigen ovalbumin (OVA) prior to immunization, we found similar induction of vaccine-induced antibody responses in mice lacking RORγt expression in Tregs compared to sufficient controls. Use of various adjuvants led to distinct findings. Our data suggest that expression of RORγt+ within Tregs is not required to regulate tolerance to systemic vaccination following oral antigen exposure., Competing Interests: The authors declare no competing interests., (© 2023 The Author(s).)

Background: The efficacy of messenger RNA (mRNA)-1273 against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection is not well defined, particularly among young adults., Methods: Adults aged 18-29 years with no known history of SARS-CoV-2 infection or prior vaccination for coronavirus disease 2019 (COVID-19) were recruited from 44 US sites from 24 March to 13 September 2021 and randomized 1:1 to immediate vaccination (receipt of 2 doses of mRNA-1273 vaccine at months 0 and 1) or the standard of care (receipt of COVID-19 vaccine). Randomized participants were followed up for SARS-CoV-2 infection measured by nasal swab testing and symptomatic COVID-19 measured by nasal swab testing plus symptom assessment and assessed for the primary efficacy outcome. A vaccine-declined observational group was also recruited from 16 June to 8 November 2021 and followed up for SARS-CoV-2 infection as specified for the randomized participants., Results: The study enrolled 1149 in the randomized arms and 311 in the vaccine-declined group and collected >122 000 nasal swab samples. Based on randomized participants, the efficacy of 2 doses of mRNA-1273 vaccine against SARS-CoV-2 infection was 52.6% (95% confidence interval, -14.1% to 80.3%), with the majority of infections due to the Delta variant. Vaccine efficacy against symptomatic COVID-19 was 71.0% (95% confidence interval, -9.5% to 92.3%). Precision was limited owing to curtailed study enrollment and off-study vaccination censoring. The incidence of SARS-CoV-2 infection in the vaccine-declined group was 1.8 times higher than in the standard-of-care group., Conclusions: mRNA-1273 vaccination reduced the incidence of SARS-CoV-2 infection from March to September 2021, but vaccination was only one factor influencing risk., Clinical Trials Registration: NCT04811664., Competing Interests: Potential conflicts of interest. All authors: No reported conflicts., (© The Author(s) 2023. Published by Oxford University Press on behalf of Infectious Diseases Society of America.)

Purpose of Review: Recent advances in the understanding of the difficult immunologic requirements for the induction of broadly neutralizing antibodies for HIV have spurred interest in optimizing vaccine approaches intended to stimulate a robust germinal center reaction. In preclinical models, techniques to optimize the germinal center response have included alterations in the timing, dose, and delivery method of immunogens and have resulted in substantially enhanced germinal center responses in lymph nodes and neutralizing antibodies in serum. One of the most promising approaches involves splitting the initial dose of vaccine into a series of gradual escalating doses administration ("fractional escalating doses"). In principle, these techniques may have broad implications for vaccines targeting a robust antibody response., Recent Findings: We review the upcoming vaccine trials that will test these concepts in clinical practice. The trials include both HIV and non-HIV immunogens, and will involve testing these concepts in both healthy adults and immunocompromised persons., Summary: There are multiple trials that will test whether techniques to alter vaccine delivery such as fractional escalating doses enhances immunologic outcomes., (Copyright © 2023 Wolters Kluwer Health, Inc. All rights reserved.)