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This study showed that a severe acute respiratory syndrome coronavirus 2 infection reduced the risk of reinfection among vaccinated individuals by 0.50 (95% CI, 0.39-0.64) over a 1-year period, after accounting for unreported infections using avidity-based serology. Reciprocally, chronic symptoms increased from a baseline of 21% (95% CI, 16%-28%) among infection-naïve individuals to 43% (95% CI, 30%-61%) in reinfected individuals., Competing Interests: Potential conflicts of interest. All authors: B.A. received honoraria for participation in live meetings from Sanofi Pasteur France and Canada related to pertussis and RSV, is a co-investigator on studies funded by GSK, Pfizer, Merck, Moderna, Vaccitech and Inventprise. All funds have been paid to his institute, and he has not received any personal payments. Other authors report no relevant conflicts to report., (© The Author(s) 2024. Published by Oxford University Press on behalf of Infectious Diseases Society of America.)

Competing Interests: Competing interests:: Bahaa Abu-Raya reports honoraria for participation in meetings from Sanofi, and is coinvestigator on studies funded by GSK, Pfizer, Merck, Moderna, Vaccitech, and Inventprise. Joanne Langley reports funding for clinical trials from GSK, Pfizer, Merck, Moderna, Sanofi, and Sequris, paid to Dalhousie University; consulting fees from GSK, Sanofi, Enanta, and Sequris, paid to departmental academic funds; and travel support from Sanofi, Enanta, and Sequris. She reports participation on a data safety monitoring board for a pneumococcal vaccine trial with Vaxcyte and the SNAP trial. She is medical advisor for the Nova Scotia Palivizumab for RSV Prevention Program and a member of a working group on influenza with the National Advisory Committee on Immunization. Pascal Lavoie is medical director of the British Columbia RSV Immunoprophylaxis Program and is employed by the Provincial Health Services Authority of British Columbia. He received honoraria for participating in an advisory board for Sanofi Canada. No other competing interests were declared.

Competing Interests: Competing interests:: Bahaa Abu-Raya reports honoraria for participation in meetings from Sanofi, and is co-investigator on studies funded by GSK, Pfizer, Merck, Moderna, Vaccitech, and Inventprise. Joanne Langley reports funding for clinical trials from GSK, Pfizer, Merck, Moderna, Sanofi, and Sequris, paid to Dalhousie University; consulting fees from GSK, Sanofi, Enanta, and Sequris, paid to departmental academic funds; and travel support from Sanofi, Enanta, and Sequris. She reports participation on a data safety monitoring board for a pneumococcal vaccine trial with Vaxcyte and the SNAP trial. She is a medical advisor for the Nova Scotia Palivizumab for RSV Prevention Program and a member of a working group on influenza with the National Advisory Committee on Immunization. Pascal Lavoie is medical director of the British Columbia RSV Immunoprophylaxis Program and is employed by the Provincial Health Services Authority of British Columbia. He received honoraria for participating in an advisory board for Sanofi Canada. No other competing interests were declared.

Detecting severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) reinfections is challenging with current serology assays and is further complicated by the marked decrease in routine viral testing practices as viral transmission increased during Omicron. Here, we provide proof-of-principle that high-avidity anti-nucleocapsid (N) antibodies detects reinfections after a single infection with higher specificity (85%; 95% confidence interval [95% CI], 80%-90%) compared to anti-N antibody levels (72%; 95% CI, 66%-79%) in a vaccinated cohort. This method could be used to retroactively investigate the epidemiology and incremental long-term health consequences of SARS-CoV-2 reinfections., Competing Interests: Potential conflicts of interest . B. A. R. has received honoraria for participation in live meetings from Sanofi Pasteur France and Canada related to pertussis and RSV, but not for this work. All other authors report no potential 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.)

Background: We recently reported a near disappearance of B. pertussis and a decline in anti-B. pertussis antibodies during the peak implementation of Coronavirus disease 2019 (COVID-19) non-pharmaceutical interventions (NPI) in 2021 in British Columbia (BC), Canada. During 2021-2023, incidence of reported B. pertussis cases remained low in BC at < 1/100,000 population. This study determined how serological evidence of B. pertussis changed after the gradual relaxation of NPI between 2021-2023., Methods: Randomly selected blood samples from school staff 25-51 years old (n = 65) were collected yearly between 2021-2023 in the Vancouver metropolitan area, BC, Canada, and tested for anti-pertussis toxin (PT) IgG levels. Serological evidence of B. pertussis infection (thereafter "seroconversion") was defined as a quantifiable anti-PT IgG levels in subjects with anti-PT IgG levels below lower limit of quantification in the preceding year or a > 4-fold increase in anti-PT IgG levels between two subsequent years. Samples were also tested for anti-diphtheria toxoid (DT) IgG, and similar seroconversion criteria were applied to exclude seroconversion due to vaccination with tetanus-diphtheria-acellular-pertussis (Tdap)., Results: Three subjects met seroconversion criteria for anti-PT IgG between 2021 and 2022 and 9 between 2022 and 2023, yielding a seroconversion rate of 4.6 /100 person-years and 14.9/100 person-years, P = 0.127, respectively. None of the subjects met the criteria for vaccination with Tdap. The geometric mean concentration of anti-PT IgG showed a statistically significant decrease in 2022 compared with 2021, 4.8 IU/mL IU/ml (95 % confidence interval [CI], 3.8-5.9) vs. 6.4 IU/ml (95 % CI, 4.9-8.2; p = 0.001), followed by a statistically significant increase in 2023 compared with 2022 6.5 IU/ml (95 % CI, 4.9-8.5) vs. 4.8 IU/ml (95 % CI, 3.8-5.9; p = 0.0006), respectively., Discussion: Serological evidence of B. pertussis increased between 2022 and 2023 despite low reported cases, which suggests that B. pertussis circulation resumed after relaxing of COVID-19 NPI., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: BA received honoraria for participation in live meetings from Sanofi Pasteur France and Canada related to pertussis and RSV., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Background: Palivizumab is recommended for prevention of severe respiratory syncytial virus (RSV) disease in immunocompromised children, despite a lack of strong supporting evidence. The recent approval of substitute RSV-neutralizing monoclonal antibodies against RSV, offers an opportunity to synthesize the most current evidence supporting the palivizumab standard of care., Objective: To evaluate the efficacy of palivizumab in preventing acute respiratory tract infection- or RSV-related hospitalization, or mortality in immunocompromised children., Methods: We searched Ovid MEDLINE and EMBASE for published clinical studies that investigated outcomes of palivizumab use in children. We included clinical trials, cohort studies, and case-control studies. The primary outcomes were RSV-related or respiratory viral infection-related hospitalizations, or RSV-related mortality. This systematic review was registered in PROSPERO (ID CRD42021248619) and is reported in accordance with the PRISMA guidelines., Results: From the 1993 records, six studies were eligible and included, for a total of 625 immunocompromised children with an heterogeneous composition of primary and acquired immunodeficiencies enrolled from palivizumab programs. There were no intervention studies. None of the studies included a control group. RSV hospitalizations were infrequent (0%-3.1% of children). Most children included received palivizumab, although one study (n = 56) did not specify how many received palivizumab. RSV mortality was neither observed, in three studies, nor reported, in three other studies., Conclusions: The evidence supporting the use of palivizumab for prevention of severe RSV disease in immunocompromised children remains extremely limited and appears insufficient to justify prioritizing this intervention as the current standard of care over alternative interventions., (© The Author(s) 2024. Published by Oxford University Press on behalf of The Journal of the Pediatric Infectious Diseases Society. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Background: Human Immunodeficiency Virus (HIV)-exposed uninfected (HEU) infants have a higher burden of infectious diseases related morbidity and mortality compared with HIV-unexposed uninfected (HUU). Immunization of pregnant women living with HIV (PWLWH) could reduce the severity and burden of infectious diseases for HEU in early infancy., Methods: We conducted a systematic review of safety and immunogenicity of vaccines administered to PWLWH and meta-analyses to test the overall effect of immunogenicity comparing pregnant women without HIV (PWWH) to PWLWH. We searched MEDLINE, Embase, Web of Science, Virtual Health Library and Cochrane databases in accordance with PRISMA guidelines for randomized controlled trials and observational studies. Review articles, case series, conference abstracts, and animal studies were excluded. Studies were included from inception to 6th September 2023, with no language restrictions. Random effects meta-analyses were performed for immunogenicity using Review manager (RevMan) analysis software version 5.4.1, Geometric Mean Titer (GMT) values were transformed to obtain the mean and standard deviation within RevMan, the effect size was computed and reported as mean difference with respective 95% confidence intervals. The review was registered with PROSPERO CRD42021289081., Findings: We included 12 articles, comprising 3744 pregnant women, 1714 were PWLWH given either influenza, pneumococcal or an investigational Group B streptococcal (GBS) vaccine. Five studies described safety outcomes, and no increase in adverse events was reported in PWLWH compared to PWWH. The GMT increase from baseline to 28-35 weeks post vaccination in HA units ranged from 12.4 (95% CI: 9.84-14.9) to 238.8 (95% CI: 0.35-477.9). Meta-analyses of influenza vaccines showed the pooled geometric mean difference in Hemagglutination Inhibition (HAI) titers post vaccination was 56.01 (95% CI: 45.01-67.01), p < 0.001. The increase was less in PWLWH when compared with PWWH: -141.76 (95% CI: -194.96, -88.55), p < 0.001., Interpretation: There are limited data on the safety and immunogenicity of vaccines given to PWLWH making policy consideration in this group difficult when new vaccines are introduced. With new vaccines on the horizon, PWLWH need to be included in studies to promote vaccine confidence for this special population., Funding: This work was funded by Medical Research Council Joint Clinical Trials Round 9 [MR/T004983/1]., Competing Interests: EN received clinical research stipend from MRC Joint Clinical Trials Round 9 [MR/T004983/1]. KLD is funded by a United Kingdom Research Institute Future Leaders Fellowship. KLD has been an investigator for projects funded by Pfizer and Minervax. All funds have been paid to her institution and she has not received personal payments of any kind. MSa is supported via salary awards from the BC Children’s Hospital Foundation and Michael Smith Health Research BC. MSa has been an investigator on projects funded by GlaxoSmithKline, Merck, Moderna, Pfizer,Sanofi-Pasteur,Seqirus, Symvivo and VBI vaccines. All funds have been paid to his institute, and he has not received any personal payments. BA has received honoraria for participation in meetings organized by Sanofi, relating to pertussis and RSV. All other authors report no conflict of interest., (© 2024 The Author(s).)

Background and Objectives: Pediatric COVID-19 cases are often mild or asymptomatic, which has complicated estimations of disease burden using existing testing practices. We aimed to determine the age-specific population seropositivity and risk factors of SARS-CoV-2 seropositivity among children and young adults during the pandemic in British Columbia (BC)., Methods: We conducted two cross-sectional serosurveys: phase 1 enrolled children and adults < 25 years between November 2020-May 2021 and phase 2 enrolled children < 10 years between June 2021-May 2022 in BC. Participants completed electronic surveys and self-collected finger-prick dried blood spot (DBS) samples. Samples were tested for immunoglobulin G antibodies against ancestral spike protein (S). Descriptive statistics from survey data were reported and two multivariable analyses were conducted to evaluate factors associated with seropositivity., Results: A total of 2864 participants were enrolled, of which 95/2167 (4.4%) participants were S-seropositive in phase 1 across all ages, and 61/697 (8.8%) unvaccinated children aged under ten years were S-seropositive in phase 2. Overall, South Asian participants had a higher seropositivity than other ethnicities (13.5% vs. 5.2%). Of 156 seropositive participants in both phases, 120 had no prior positive SARS-CoV-2 test. Young infants and young adults had the highest reported seropositivity rates (7.0% and 7.2% respectively vs. 3.0-5.6% across other age groups)., Conclusions: SARS-CoV-2 seropositivity among unvaccinated children and young adults was low in May 2022, and South Asians were disproportionately infected. This work demonstrates the need for improved diagnostics and reporting strategies that account for age-specific differences in pandemic dynamics and acceptability of testing mechanisms., (© 2024. The Author(s).)

Neither immunization nor recovery from natural infection provides life-long protection against Bordetella pertussis. Replacement of a whole-cell pertussis (wP) vaccine with an acellular pertussis (aP) vaccine, mutations in B. pertussis strains, and better diagnostic techniques, contribute to resurgence of number of cases especially in young infants. Development of new immunization strategies relies on a comprehensive understanding of immune system responses to infection and immunization and how triggering these immune components would ensure protective immunity. In this review, we assess how B cells, and their secretory products, antibodies, respond to B. pertussis infection, current and novel vaccines and highlight similarities and differences in these responses. We first focus on antibody-mediated immunity. We discuss antibody (sub)classes, elaborate on antibody avidity, ability to neutralize pertussis toxin, and summarize different effector functions, i.e. ability to activate complement, promote phagocytosis and activate NK cells. We then discuss challenges and opportunities in studying B-cell immunity. We highlight shared and unique aspects of B-cell and plasma cell responses to infection and immunization, and discuss how responses to novel immunization strategies better resemble those triggered by a natural infection (i.e., by triggering responses in mucosa and production of IgA). With this comprehensive review, we aim to shed some new light on the role of B cells and antibodies in the pertussis immunity to guide new vaccine development., Competing Interests: Declaration of Competing Interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: ‘BA has received honoraria for participation in meetings organized by Sanofi, relating to pertussis and RSV. MS has been an investigator on projects funded by GlaxoSmithKline, Merck, Moderna, Pfizer, Sanofi-Pasteur, Seqirus, Symvivo and VBI Vaccines. All funds have been paid to his institute, and he has not received any personal payments. SH has been an investigator on projects funded by GlaxoSmithKline, Merck, Moderna, Pfizer, Sanofi-Pasteur, Seqirus, CanSino, Entos, and VBI Vaccines. All funds have been paid to his institute, and he has not received any personal payments.’., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Studies have linked respiratory syncytial virus (RSV) antibody-mediated phagocytosis and complement deposition to severe RSV infection in humans. This study shows waning of these antibody functions in women of childbearing age in 2020-2021 during the implementation of COVID-19 mitigation measures, in absence of RSV circulation. These functions could be explored as correlates of protection against severe RSV disease., (© The Author(s) 2023. Published by Oxford University Press on behalf of The Journal of the Pediatric Infectious Diseases Society. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Background: The COVID-19 pandemic has perturbed the seasonality of respiratory syncytial virus (RSV) infections. However, we lack data on how this impacted the severity of paediatric RSV cases. The objective of this study was to describe the clinical severity of RSV cases before, during and after pandemic measures in British Columbia (BC), Canada., Methods: Retrospective study of RSV cases from September 1st, 2017 to May 15th, 2023, with a review of RSV outcomes in children below 18 years old at BC's paediatric hospital. Temporal changes in RSV cases and hospitalisations were quantified using interrupted time series., Findings: BC experienced only 11 RSV cases (from 95,266 tests) between September 2020 and August 2021. This was followed by a resurgence of 9,529 RSV cases (219,566 tests [4.3% positive tests]) in 2021-22 and 8,215 cases (124,449 tests [6.6% positive tests]) in 2022-23, increased compared to 1,750 cases (48,664 tests [3.6% positive tests]) per corresponding yearly period in 2017-20. From September 2017 to May 2023, the median age of children with RSV at BC Children's Hospital increased from 8.7 [IQR: 2.0-26.0] to 19.6 [3.9-43.7] months per yearly period. More children were hospitalised in 2022-23 (n = 360), compared to 2017-20 (n = 168 per period) and 2021-22 (n = 172). However, we detected no increase in hospitalisations or ICU admissions in children born prematurely or with chronic cardiorespiratory conditions., Interpretation: The increased detection of symptomatic RSV cases in older children in 2021-22 and increased RSV-related hospitalisations in 2022-23 suggest a gradual increase in the pool of immunologically vulnerable children due to a prolonged lack of viral exposure., Funding: Government of Canada via its COVID-19 Immunity Task Force., Competing Interests: PML received an honorarium from Sanofi, for participation on advisory board meetings. BA received honoraria for participation in live meetings from Sanofi Pasteur France and Canada related to pertussis (for BA) and RSV products, but not related to this study. JAS received grants from WorkSafe BC, BC Children's Hospital Research Institute, and COVID-19 Immunity Task Force, which were not related to this study. DMG received a grant from bioMerieux Inc. as investigator-initiated research for a blood culture study, not related to this study. DMS received grants from Michael Smith Foundation for Health Research, Canadian Institutes of Health Research, Public Agency of Canada, and BCCDC Foundation for public health which were not related to this study. Other authors declare no other relevant conflicts of interest., (© 2023 The Author(s).)

The coronavirus disease 2019 (COVID-19) pandemic has drastically perturbed the epidemiology of Respiratory Syncytial Virus (RSV) respiratory tract infections in children. The reasons for this are not clear. In this article, we review the current literature and critically discuss the different theories to explain why the epidemiology of RSV has changed during the COVID-19 pandemic. Proposed mechanisms include decreased viral immunity in vulnerable age groups caused by the prolonged lack of RSV circulation early in the pandemic, potential Severe Acute Respiratory Syndrome Corona Virus 2 (SARS-CoV-2)-induced immune dysregulation, viral interactions between SARS-CoV-2 and RSV, and modifications in health-seeking behaviors as well as heath systems factors. Research in viral genomics and phylogeny, and more robust immunology research is needed to guide RSV prevention and health care resource planning., Competing Interests: BA received honoraria for participation in live meetings from Sanofi Pasteur France and Canada related to pertussis (for BA) and RSV products, but not related to this study. PML received honoraria for participating in an Advisory Board meeting for Sanofi Canada, unrelated to this study. Other authors have no conflicts of interest to declare., (© 2023 The Author(s).)

Health jurisdictions have seen a near-disappearance of respiratory syncytial virus (RSV) during the first year of the coronavirus disease 2019 (COVID-19) pandemic. Over this corresponding period, we report a reduction in RSV antibody levels and live virus neutralization in sera from women of childbearing age and infants between May to June 2020 and February to June 2021, in British Columbia (BC), Canada. This supports that antibody immunity against RSV is relatively short-lived and that maintaining optimal antibody levels in infants requires repeated maternal viral exposure. Waning immunity may explain the interseasonal resurgence of RSV cases observed in BC and other countries., Competing Interests: Potential conflicts of interest . 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. PML serves on the British Columbia RSV Immunoprophylaxis Program, a publicly funded program under the British Columbia Ministry of Health and Provincial Health Services Authority. Other authors declare no relevant conflicts of interest., (© The Author(s) 2022. Published by Oxford University Press on behalf of Infectious Diseases Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

The highest morbidity and mortality from respiratory syncytial virus (RSV) infection occurs in young infants. Immunization of expectant mothers during pregnancy has the potential to substantially reduce the burden of RSV disease in a majority of infants. Correlates of protection (COP) are important in guiding the development of maternal RSV vaccines and the design of maternal RSV vaccine trials, as immune response to candidate vaccines should mirror protective RSV immunity at birth. Here, we review the literature reporting correlations between RSV immune measures at birth and clinical RSV outcomes during infancy. Less than a dozen studies have investigated immunological COP with RSV disease or related hospitalization, yielding inconsistent findings overall. The differences in findings between studies could be due to differences in inclusion/exclusion criteria (e.g., the inclusion of older infants who may benefit less from maternal antibodies or infants followed during inter-seasonal periods where RSV is absent), differences in semi-quantitative RSV antibody neutralization assays, or differences in RSV outcome measures such as the sensititivity/specificity of diagnostic tests. Future research in this field should seek to standardize RSV immunological measures and outcomes, expand the breadth of functional RSV measures beyond antibody neutralization, and consider infants' age and seasonality of RSV infection., (© 2022. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Infants are at high risk for severe morbidity and mortality from pertussis disease during early infancy. Vaccination against pertussis in pregnancy has emerged as the ideal strategy to protect infants during these early, vulnerable, first months of life. On 30 November and 1 December 2021, the Global Pertussis Initiative held a meeting that aimed to discuss and review the most up-to-date scientific literature supporting vaccination against pertussis in pregnancy and outstanding scientific questions. Herein, we review the current and historically published literature and summarize the findings as consensus statements on vaccination against pertussis in pregnancy on behalf of the Global Pertussis Initiative.

Competing Interests: Declaration of Competing Interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: MS is supported via salary awards from the BC Children’s Hospital Foundation, the Canadian Child Health Clinician Scientist Program and the Michael Smith Foundation for Health Research. MS has been an investigator on projects funded by GlaxoSmithKline, Merck, Pfizer, Sanofi-Pasteur, Seqirus, Symvivo and VBI Vaccines. All funds have been paid to his institute, and he has not received any personal payments. All other authors declare no competing interest. SH has been an investigator on projects funded by GlaxoSmithKline, Merck, Pfizer, Sanofi-Pasteur, and CanSino; all funds have been paid to his University. SH has also served on ad hoc advisory boards for GSK, Sanofi, Pfizer, AsraZeneca, Merck, and IMV. .

Background: Immunization against Bordetella pertussis during pregnancy reduces morbidity from severe pertussis in young infants via trans-placental transfer of anti-B. pertussis Immunoglobulin G (IgG). Studies have reported a near disappearance of respiratory pathogens including B. pertussis following implementation of mitigation strategies to control Coronavirus disease 2019 (COVID-19). We explored how immunity against B. pertussis changed in women of childbearing-age through the COVID-19 pandemic., Methods: Paired blood samples from females of childbearing-age collected at the beginning (May-June 2020) and nearly one year into the COVID-19 pandemic (February-May 2021) in British Columbia (BC), Canada were tested for anti-B. pertussis IgG levels. To ascertain whether early-pandemic IgG levels in 2020 reflected levels in pregnant women early in gestation, 1st trimester sera collected from age-matched healthy pregnant women in 2018 and 2019 were tested for anti-B. pertussis IgG. Levels were compared by t tests. P-value of 0.05 was assigned and statistical significance was set as p < 0.016 using Bonferroni correction., Results: Annual provincial B. pertussis incidences per 100,000 in BC in 2020 (3/100,000) and 2021 (<1/100,000) approximated the lowest levels since 1990. In 2021 vs. 2020, anti-pertussis toxin (PT), filamentous hemagglutinin (FHA) and pertactin (PRN) IgG levels declined in women of childbearing-age: 6.8 IU/ml (95 %CI, 4.2-10.9) vs. 8.4 IU/ml (5.1-13.9; p = 0.004); 18.8 IU/ml (10.9-32.2) vs. 23.6 IU/ml (13.2-42.1; p < 0.001); and 37.1 IU/ml (18.1-75.9) vs. 47.2 IU/ml (24.8-89.9; p = 0.092), respectively. Although all values were slightly higher, anti-PT, FHA and PRN IgG levels in women of childbearing age did not significantly differ in 2020 compared with early-gestation pregnant women in 2018-2019, 8.4 IU/ml (95% CI, 5.1-13.9) vs. 5.4 IU/ml (95% CI, 3.8-7.7; p = 0.166), 23.6 IU/ml (95% CI, 13.2-42.1) vs. 20.1 IU/ml (95% CI, 13.4-30.2; p = 0.656), and 47.2 IU/ml (24.8-89.9) vs. 17.3 IU/ml (95% CI, 10.5-28.7; p = 0.021), respectively., Discussion: B. pertussis infections should be closely monitored during the relaxing of mitigation measures for COVID-19., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Respiratory syncytial virus (RSV) causes a spectrum of respiratory illnesses in infants and young children that may lead to hospitalizations and a substantial number of outpatient visits, which result in a huge economic and healthcare burden. Most hospitalizations happen in otherwise healthy infants, highlighting the need to protect all infants against RSV. Moreover, there is evidence on the association between early-life RSV respiratory illness and recurrent wheezing/asthma-like symptoms As such, RSV is considered a global health priority. However, despite this, the only prevention strategy currently available is palivizumab, a monoclonal antibody (mAb) indicated in a subset of preterm infants or those with comorbidities, hence leaving the majority of the infant population unprotected against this virus. Therefore, development of prevention strategies against RSV for all infants entering their first RSV season constitutes a large unmet medical need. The aim of this review is to explore different immunization approaches to protect all infants against RSV. Prevention strategies include maternal immunization, immunization of infants with vaccines, immunization of infants with licensed mAbs (palivizumab), and immunization of infants with long-acting mAbs (e.g., nirsevimab, MK-1654). Of these, palivizumab use is restricted to a small population of infants and does not offer a solution for all-infant protection, whereas vaccine development in infants has encountered various challenges, including the immaturity of the infant immune system, highlighting that future pediatric vaccines will most likely be used in older infants (>6 months of age) and children. Consequently, maternal immunization and immunization of infants with long-acting mAbs represent the two feasible strategies for protection of all infants against RSV. Here, we present considerations regarding these two strategies covering key areas which include mechanism of action, "consistency" of protection, RSV variability, duration of protection, flexibility and optimal timing of immunization, benefit for the mother, programmatic implementation, and acceptance of each strategy by key stakeholders. We conclude that, based on current data, immunization of infants with long-acting mAbs might represent the most effective approach for protecting all infants entering their first RSV season., Competing Interests: SE: Speaker’s fees from GSK, Pfizer, Novartis, Sanofi Pasteur, MSD and Vifor in the past three years. BA is supported by the Michael Smith Foundation for Health Research and received payment as a scientific expert of the Sanofi group of companies. KF is a member of the Australian Technical Advisory Group on Immunisation noting that this paper represents her own personal view; received honoraria as a member of the vaccine advisory boards for Seqiris and Sanofi Pasteur in the last 5 years. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Esposito, Abu Raya, Baraldi, Flanagan, Martinon Torres, Tsolia and Zielen.)

Background: Exploring factors that affect immune responses to immunizations in infants born to women immunized with tetanus-diphtheria-acellular-pertussis (Tdap) in pregnancy compared with unimmunized women is important in designing immunization programs., Methods: Individual-participant data meta-analysis of 8 studies reporting post-immunization immunoglobulin G (IgG) levels to vaccine antigens in infants born to either women immunized with Tdap in pregnancy or unimmunized women, using mixed-effects models., Results: In infants of Tdap-immunized women, two-fold higher levels of anti-pertussis toxin (PT) and anti-diphtheria-toxoid (DT) IgG pre-primary immunization were associated with 9% and 10% lower post-primary immunization levels, (geometric mean ratio [GMR], PT: 0.91; 95% CI, 0.88-0.95,n = 494, DT: 0.9; 0.87-0.93,n = 519). Timing of immunization in pregnancy did not affect post-primary immunization anti-Bordetella pertussis, anti-tetanus-toxoid (TT) and anti-DT IgG levels. Spacing of infant immunization did not affect post-primary immunization anti-B. pertussis and anti-DT levels. In infants of Tdap-immunized women, two-fold higher levels of anti-PT and anti-filamentous haemagglutinin (FHA) IgG pre-primary immunization were associated with lower post-booster immunization levels, (GMR, PT: 0.91; 0.85-0.97,n = 224, FHA: 0.92; 0.85-0.99,n = 232). Timing of immunization in pregnancy did not affect post-booster immunization anti-Bordetella pertussis, anti-tetanus-toxoid (TT) and anti-DT IgG levels. Spacing of infant immunization did not affect post-booster immunization anti-PT, anti-pertactin (PRN), anti-TT and anti-DT IgG levels. In infants of unimmunized women, two-fold higher IgG levels of some vaccine antigens pre-primary immunization were associated with 8-17% lower post-primary immunization levels (GMR, PT 0.92, 95% CI:0.88-0.97, n = 373; FHA:0.88, 95% CI:0.85-0.92,n = 378; PRN:0.84, 95% CI:0.81-0.88, n = 367; TT:0.88, 95% CI:0.83-0.93, n = 241; DT: 0.83, 95% CI:0.79-0.87,n = 278). Two-fold higher levels of anti-FHA IgG pre-primary immunization were associated with 8% lower post-booster immunization levels (GMR, 0.92; 95% CI: 0.86-0.99,n = 138)., Discussion: Increased IgG levels pre-primary immunization is associated with reduced post-primary and post-booster immunization levels for some antigens in infants of women immunized or unimmunized in pregnancy, but their clinical significance is uncertain., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Pregnant women are at increased risk for severe morbidity and mortality following infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), leading some countries to recommend vaccination of pregnant women against coronavirus disease 2019 (COVID-19). These recommendations are based on studies conducted early in the pandemic, and thus, the pregnant women in these studies most likely did not have pre-existing immunity to SARS-CoV-2 at the time of infection. The susceptibility of pregnant women and their infants to SARS-CoV-2 and the severity of infection may be attenuated as the pandemic progresses and an increasing number of women will have pre-existing immunity (following natural infection or vaccination prior to pregnancy) during pregnancy. The reactogenicity, immunogenicity and efficacy of COVID-19 vaccines administered in pregnancy may also be affected by the pre-existing immunity of pregnant women. Maternal vaccine trials should be evaluated in the context of their timing in the pandemic and interpreted based on the pre-existing immunity of pregnant women., (Copyright © 2021 by the American Academy of Pediatrics.)

Routine childhood vaccinations are key for the protection of children from a variety of serious and potentially fatal diseases. Current pediatric vaccine schedules mainly cover active vaccines. Active vaccination in infants is a highly effective approach against several infectious diseases; however, thus far, for some important viral pathogens, including respiratory syncytial virus (RSV), vaccine development and license by healthcare authorities have not been accomplished. Nirsevimab is a human-derived, highly potent monoclonal antibody (mAb) with an extended half-life for RSV prophylaxis in all infants. In this manuscript, we consider the potential implications for the introduction of an anti-viral mAb, such as nirsevimab, into the routine pediatric vaccine schedule, as well as considerations for coadministration. Specifically, we present evidence on the general mechanism of action of anti-viral mAbs and experience with palivizumab, the only approved mAb for the prevention of RSV infection in preterm infants, infants with chronic lung disease of prematurity and certain infants with hemodynamically significant heart disease. Palivizumab has been used for over two decades in infants who also receive routine vaccinations without any alerts concerning the safety and efficacy of coadministration. Immunization guidelines (Advisory Committee on Immunization Practices, Joint Committee on Vaccination and Immunization, National Advisory Committee on Immunization, Centers for Disease Control and Prevention, American Academy of Pediatrics, The Association of the Scientific Medical Societies in Germany) support coadministration of palivizumab with routine pediatric vaccines, noting that immunobiologics, such as palivizumab, do not interfere with the immune response to licensed live or inactivated active vaccines. Based on the mechanism of action of the new generation of anti-viral mAbs, such as nirsevimab, which is highly specific targeting viral antigenic sites, it is unlikely that it could interfere with the immune response to other vaccines. Taken together, we anticipate that nirsevimab could be concomitantly administered to infants with routine pediatric vaccines during the same clinic visit., Competing Interests: SE: Research support from GSK, Sanofi, and Vifor. Speaker’s fees from GSK, Janssen, Pfizer, Novartis, Sanofi Pasteur, and MSD in the past 3 years. BA is supported by the Canadian Health and Research Institute Vanier Canada scholarship. PB received grants for epidemiological and HTA research projects from GlaxoSmithKline, MSD, Sanofi Pasteur, Pfizer, Seqirus and Astra Zeneca, and fees for taking part in advisory boards on different vaccines from the same companies plus Janssen. FM has received honoraria from GSK, Pfizer, Sanofi Pasteur, MSD, Seqirus, and Janssen for taking part in advisory boards and expert meetings, and for acting as speaker in congresses outside the scope of the submitted work. FM has also acted as principal investigator in RCTs of the above-mentioned companies as well as Ablynx, Regeneron, Roche, Abbot, Novavax, and Medimmune, with honoraria paid to his institution. FM research activities received support from the Instituto de Salud Carlos III (Proyecto de Investigación en Salud, Acción Estratégica en Salud): project ReSVinext ISCIII/PI16/01569/Cofinanciado FEDER and project Enterogen (ISCIII/PI19/01090). KF is a member of the Australian Technical Advisory Group on Immunisation (ATAGI) but the views in this manuscript are her own and not necessarily those of ATAGI. KF has received honoraria as a member of the vaccine advisory boards for Seqiris and Sanofi Pasteur in the last 5 years. AM has received research grants from NIH, Janssen and Merck AND fees for participation in advisory boards from Janssen, Sanofi-Pasteur, Merck and Roche. MS reports research grants and personal fees for advisory boards from GSK, Pfizer, Sanofi-Pasteur, Janssen and Seqirus. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Esposito, Abu-Raya, Bonanni, Cahn-Sellem, Flanagan, Martinon Torres, Mejias, Nadel, Safadi and Simon.)

Background: Immunization with tetanus-diphtheria-acellular pertussis (Tdap) vaccine in pregnancy is increasingly recommended. We determined the effect of Tdap immunization in pregnancy on infants' vaccine responses., Methods: Individual-participant data meta-analysis of ten studies (n=1884) investigating infants' antibody response to routine immunizations following Tdap immunization in pregnancy was performed. Geometric mean ratios (GMRs) of antigen-specific immunoglobulin G (IgG) levels were calculated using mixed-effects models. Seroprotection rates were compared using chi-squared tests., Results: Infants of Tdap-immunized women had significantly lower IgG against pertussis toxin (GMR 0.65; 95%CI 0.57-0.74), filamentous haemagglutinin (FHA) (0.68; 0.53-0.87), pertactin (0.65; 0.58-0.72) and fimbria 2/3 (FIM2/3) (0.41; 0.32-0.52) after primary immunization, compared with infants of unimmunized women. These lower levels persisted after booster immunization for FHA (0.72; 0.61-0.84) and FIM2/3 (0.53; 0.29-0.96). After primary immunization, infants of Tdap-immunized women had lower seroprotection rates against diphtheria (90% [843/973] vs 98% [566/579]; p<0.001) and invasive pneumococcal disease (IPD) caused by 5 Streptococcus pneumoniae (SPN) serotypes (SPN5, SPN6B, SPN9V, SPN19A, SPN23F), and higher seroprotection rates against Haemophilus influenzae type b (short-term and long-term seroprotection rates, 86%[471/547] vs 76%[188/247] and 62%[337/547] vs 49%(121/247), respectively, all p=0.001). After booster immunization, seroprotection rates against diphtheria and tetanus were 99% (286/288) and (618/619) in infants of Tdap-immunized women, respectively., Conclusions: Infants of Tdap-immunized women in pregnancy had lower IgG levels against pertussis, diphtheria and some SPN serotypes after their immunization compared with infants of unimmunized women. Enhanced surveillance of pertussis, diphtheria and IPD in infants is needed to determine the clinical significance of these findings., Systematic Review Registration: CRD42017079171., Competing Interests: BA-R is supported by the Canadian Health and Research Institute Vanier Canada Graduate scholarship. KM is the beneficiary of a postdoctoral mandate fellowship from the Fund for Scientific Research-Flanders (FWO 12R5819). MS is supported via salary awards from the BC Children’s Hospital Foundation, the Canadian Child Health Clinician Scientist Program and the Michael Smith Foundation for Health Research. MS has been an investigator on projects funded by GlaxoSmithKline, Merck, Pfizer, Sanofi Pasteur, Seqirus, Symvivo and VBI Vaccines. All funds have been paid to his institute, and he has not received any personal payments. SH has been an investigator on projects funded by GlaxoSmithKline, Merck, Pfizer, Sanofi-Pasteur, and CanSino; all funds have been paid to his University. SH has also served on ad hoc advisory boards for GSK, Sanofi, Pfizer, AsraZeneca, Merck, and IMV. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Abu-Raya, Maertens, Munoz, Zimmermann, Curtis, Halperin, Rots, Barug, Holder, Kampmann, Leuridan and Sadarangani.)

Objectives: International data on listeriosis during infancy from large populations are essential to guide evidence-based empiric antibiotic guidelines for sepsis in infancy. We aimed to determine the incidence, clinical manifestations, and outcome of listeriosis in infants <6 months of age in Canada and Switzerland., Methods: Prospective, active surveillance of listeriosis in infants <6 months of age was conducted through the Canadian Paediatric Surveillance Program (May 2015 to April 2017) and the Swiss Paediatric Surveillance Unit (April 2017 to March 2018). Confirmed and probable cases were included., Results: In Canada, eight sporadic listeriosis cases were reported (incidence, 1.1/100,000 live births/year). In Switzerland, four cases were reported (incidence, 4.5/100,000 live births/year) of which three were part of a confirmed outbreak with an unclear source. In the two countries, eight of the 12 cases (66.6%) presented as early-onset disease (within the first 7 days of life) and none presented after 28 days life., Conclusions: Neonatal listeriosis is rare. Infants presenting with sepsis, especially after 4 weeks of life, may not routinely require empiric antibiotic coverage for listeriosis. Outbreak-related cases still occur. Continued surveillance is important., (© The Author(s) 2021. Published by Oxford University Press on behalf of the Canadian Paediatric Society. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Importance: An effective vaccine against SARS-CoV-2 will reduce morbidity and mortality and allow substantial relaxation of physical distancing policies. However, the ability of a vaccine to prevent infection or disease depends critically on protecting older individuals, who are at highest risk of severe disease., Objective: We quantitatively estimated the relative benefits of COVID-19 vaccines, in terms of preventing infection and death, with a particular focus on effectiveness in elderly people., Design: We applied compartmental mathematical modelling to determine the relative effects of vaccines that block infection and onward transmission, and those that prevent severe disease. We assumed that vaccines showing high efficacy in adults would be deployed, and examined the effects of lower vaccine efficacy among the elderly population., Setting and Participants: Our mathematical model was calibrated to simulate the course of an epidemic among the entire population of British Columbia, Canada. Within our model, the population was structured by age and levels of contact., Main Outcome(s) and Measure(s): We assessed the effectiveness of possible vaccines in terms of the predicted number of infections within the entire population, and deaths among people aged 65 years and over., Results: In order to reduce the overall rate of infections in the population, high rates of deployment to all age groups will be critical. However, to substantially reduce mortality among people aged 65 years and over, a vaccine must directly protect a high proportion of people in that group., Conclusions and Relevance: Effective vaccines deployed to a large fraction of the population are projected to substantially reduce infection in an otherwise susceptible population. However, even if transmission were blocked highly effectively by vaccination of children and younger adults, overall mortality would not be substantially reduced unless the vaccine is also directly protective in elderly people. We strongly recommend: (i) the inclusion of people aged 65 years and over in future trials of COVID-19 vaccine candidates; (ii) careful monitoring of vaccine efficacy in older age groups following vaccination., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Newborns and infants are at risk for severe infections with some pathogens (eg, Bordetella pertussis , influenza, respiratory syncytial virus, group B Streptococcus ) during early life. To decrease this window of high susceptibility to some infections during early life and protect young infants, vaccination in pregnancy against some vaccine-preventable diseases (eg, influenza, pertussis, tetanus) has been recommended in an increasing number of countries with notable success. In addition, recent advances have been made in developing vaccines for pregnant women with the aim of reducing the respiratory syncytial virus and group B Streptococcus burden in infancy. In this article, we review the vaccines currently recommended during pregnancy and their benefits to newborns and infants. We also discuss progress made in the development of other vaccines that are expected to be evaluated in pregnant women in the near future., (Copyright © 2021 by the American Academy of Pediatrics.)

In this study, we illustrate, for the first time, that preexisting low-avidity neutralizing measles maternal antibodies do not interfere with the development of high concentrations of high-avidity measles antibodies in children immunized at age 12 months. This suggests that the quality of measles maternal antibodies, rather than the quantity, impacts immunogenicity of primary measles immunization., (© The Author(s) 2019. Published by Oxford University Press on behalf of The Journal of the Pediatric Infectious Diseases Society. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Competing Interests: Intérêts concurrents: Soren Gantt reçoit des honoraires de consultant de Moderna, de Merck, de GlaxoSmithKline et de Curevo; du financement pour la recherche sur les vaccins de Merck, de GlaxoSmithKline et de VBI Vaccines; et du financement pour l’essai d’un vaccin contre la COVID-19 de Symvivo. Soren Gantt est également membre ayant droit de vote du Comité consultatif national de l’immunisation. Manish Sadarangani a pris part à des projets de recherche financés par Pfizer, Merck, Seqirus, Sanofi Pasteur, VBI Vaccines et GlaxoSmithKline, et a reçu du financement pour l’essai d’un vaccin contre la COVID-19 de Symvivo. Tous les fonds ont été versés à son établissement; il n’a reçu aucun honoraire personnel. Aucun autre intérêt concurrent n’a été déclaré.

Coronavirus disease 2019 (COVID-19) is a rapidly evolving, highly transmissible, and potentially lethal pandemic caused by a novel coronavirus, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). As of June 11 2020, more than 7,000,000 COVID-19 cases have been reported worldwide, and more than 400,000 patients have died, affecting at least 188 countries. While literature on the disease is rapidly accumulating, an integrated, multinational perspective on clinical manifestations, immunological effects, diagnosis, prevention, and treatment of COVID-19 can be of global benefit. We aimed to synthesize the most relevant literature and experiences in different parts of the world through our global consortium of experts to provide a consensus-based document at this early stage of the pandemic., (Copyright © 2020 Abu-Raya, Migliori, O'Ryan, Edwards, Torres, Alffenaar, Märtson, Centis, D'Ambrosio, Flanagan, Hung, Lauretani, Leung, Leuridan, Maertens, Maggio, Nadel, Hens, Niesters, Osterhaus, Pontali, Principi, Rossato Silva, Omer, Spanevello, Sverzellati, Tan, Torres-Torreti, Visca and Esposito.)

Background: The Canadian National Advisory Committee on Immunization recommends universal vaccination against pertussis in pregnancy. We assessed the cost-effectiveness of vaccination with tetanus-diphtheria-acellular pertussis (Tdap) vaccine in pregnancy in Canada., Methods: We conducted a cost-utility analysis comparing a vaccination program to no program corresponding with the 2017 Canadian guideline for economic evaluation from the Canadian Agency for Drugs and Technologies in Health. We developed 2 models - part decision tree, part Markov model - to estimate the long-term cost and quality-adjusted life-years (QALYs) for pregnant women and their infants. We obtained epidemiologic data from 2006 to 2015, and derived costs and utility values from relevant sources. Results were reported in 2019 Canadian dollars. We obtained expected values through probabilistic analysis, with methodologic and structural uncertainty assessed through scenario analyses. The analysis adopted an acquisition price of Tdap vaccine of $12.50, with scenario analysis conducted to identify the threshold price for vaccination to be cost-effective., Results: In the base-case scenario, for every 1000 pregnant women vaccinated, the program would lead to a gain of 0.3 QALYs, occurring solely in infants, at an increased total cost of $12 987, or $44 301 per QALY gained. Based on a threshold of $50 000 per QALY gained, vaccination would have been cost-effective in 6 of the 10 years included in the model (range of incremental costs $20 463-$100 348 per QALY gained). The threshold cost for Tdap vaccine to be cost-effective over the 10-year horizon was $14.03., Interpretation: Based on a threshold of $50 000 per QALY gained, vaccination against pertussis in pregnancy would be cost-effective if the acquisition cost per vaccine were $14.03 or less. Province- and territory-specific analyses should be done to inform local decision-making., Competing Interests: Competing interests: Manish Sadarangani is supported via salary awards from the BC Children’s Hospital Foundation, the Canadian Child Health Clinician Scientist Program and the Michael Smith Foundation for Health Research. He has been an investigator on projects funded by Merck, VBI Vaccines, Pfizer, Seqirus, Sanofi Pasteur and GlaxoSmithKline; all funds have been paid to his institute, and he has not received any personal payments. Scott Halperin has been an investigator on projects funded by Merck, VBI Vaccines, Pfizer, Seqirus, Sanofi Pasteur and GlaxoSmithKline, and has served on ad hoc advisory boards for Merck, Sanofi Pasteur, GlaxoSmithKline and Pfizer; all funds have been paid to his university, and he has not received any personal payments. No other competing interests were declared., (Copyright 2020, Joule Inc. or its licensors.)

The risk and severity of specific infections are increased during pregnancy due to a combination of physiological and immunological changes. Characterizing the maternal immune system during pregnancy is important to understand how the maternal immune system maintains tolerance towards the allogeneic fetus. This may also inform strategies to prevent maternal fatalities due to infections and optimize maternal vaccination to best protect the mother-fetus dyad and the infant after birth. In this review, we describe what is known about the immunological changes that occur during a normal pregnancy., (Copyright © 2020 Abu-Raya, Michalski, Sadarangani and Lavoie.)

Competing Interests: POTENTIAL CONFLICT OF INTEREST: Dr Edwards serves as an advisor for Bionet and Merck and on data safety and monitoring boards for Sanofi, X4 Pharmaceuticals, Seqirus, Moderna, and Pfizer; and Dr Abu-Raya has indicated he has no potential conflicts of interest to disclose.

Competing Interests: Competing interests: Soren Gantt receives consulting fees related to vaccines from Moderna, Merck, GlaxoSmithKline and Curevo; research funding for vaccine research from Merck, GlaxoSmithKline and VBI; and research funding for a COVID-19 vaccine trial from Symvivo. Soren Gantt is also a voting member of the Canadian National Advisory Committee on Immunization. Manish Sadarangani has been an investigator on projects funded by Pfizer, Merck, Seqirus, Sanofi Pasteur, VBI Vaccines and GlaxoSmithKline, and has received research funding for a COVID-19 vaccine trial from Symvivo. All funds have been paid to his institution, and he has not received any personal payments. No other competing interests were declared.