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BACKGROUND Infants younger than 6 months of age are at high risk for complications of coronavirus disease 2019 (Covid-19) and are not eligible for vaccination. Transplacental transfer of .antibodies against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) after maternal Covid-19 vaccination may confer protection against Covid-19 in infants. METHODS We used a case-control test-negative design to assess the effectiveness of maternal vaccination during pregnancy against hospitalization for Covid-19 among infants younger than 6 months of age. Between July 1 2021 and March 8,2022 we enrolled infants hospitalized for Covid-19 (case infants) and infants hospitalized without Covid-19 (control infants) at 30 hospitals in 22 states. We estimated vaccine effectiveness by comparing the odds of full maternal vaccination (two doses of mRNA vaccine) among case infants and control infants during circulation of the B.1.6172 (delta) variant (July 1 2021 to December 18 2021) and the B.1.1.259 (omicron) variant (December 19, 2021, to March 8, 2022). RESULTS A total of 537 case infants (181 of whom had been admitted to a hospital during the delta period and 356 during the omicron period; median age 2 months) and512 control infants were enrolled and included in the analyses; 16°/0 of the case infants and 29 of the control infants had been born to mothers who had been fully vaccinated against Covid-19 during pregnancy. Among the case infants 113 (21%) received intensive care (64 [1296] received mechanical ventilation or vasoactive infusions). Two case infants died from Covid-19; neither infant's mother had been vaccinated during pregnancy. The effectiveness of maternal vaccination against hospitalization for Covid-19 among infants was 52% (95 confidence interval ICI] 33 to 65) overall 80% (95% CI 60 to 90) during the delta period and 38% (95% CI 8 to 58) during the omicron period. Effectiveness was 6996 (95% CI,50 to 80) when maternal vaccination occurred after 20 weeks of pregnancy and 38% (95% CI 3 to 60) during the first 20 weeks of pregnancy. CONCLUSIONS Maternal vaccination with two doses of mRNA vaccine was associated with a reduced risk of hospitalization for Covid-19 including for critical illness among infants young- er than 6 months of age. (Funded by the Centers for Disease Control and Prevention.) [ABSTRACT FROM AUTHOR]

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BACKGROUND The increasing incidence of pediatric hospitalizations associated with coronavirus disease 2019 (Covid-19) caused by the B.1.617.2 (delta) variant of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in the United States has offered an opportunity to assess the real-world effectiveness of the BNT162b2 messenger RNA vaccine in adolescents between 12 and 18 years of age. METHODS We used a case-control, test-negative design to assess vaccine effectiveness against Covid-19 resulting in hospitalization, admission to an intensive care unit (ICU), the use of life-supporting interventions (mechanical ventilation, vasopressors, and extra-corporeal membrane oxygenation), or death. Between July 1 and October 25, 2021, we screened admission logs for eligible case patients with laboratory-confirmed Covid-19 at 31 hospitals in 23 states. We estimated vaccine effectiveness by comparing the odds of antecedent full vaccination (two doses of BNT162b2) in case patients as compared with two hospital-based control groups: patients who had Covid-19-like symptoms but negative results on testing for SARS-CoV-2 (test-negative) RESULTS and patients who did not have Covid-19-like symptoms (syndrome-negative). A total of445 case patients and 777 controls were enrolled. Overall, 17 case patients (490) and 282 controls (36°6) had been fully vaccinated. Of the case patients, 180 (40°6) were admitted to the ICU, and 127 (29°/0) required life support; only 2 patients in the ICU had been fully vaccinated. The overall effectiveness of the BNT162b2 vaccine against hospitalization for Covid-19 was 94% (95% confidence interval [CI], 90 to 96); the effectiveness was 95% (95% CI, 91 to 97) among test-negative controls and 94% (95% CI, 89 to 96) among syndrome-negative controls. The effectiveness was 98% against ICU admission and 98°/0 against Covid-19 resulting in the receipt of life support. All 7 deaths occurred in patients who were unvaccinated. CONCLUSIONS Among hospitalized adolescent patients, two doses of the BNT162b2 vaccine were highly effective against Covid-19-related hospitalization and ICU admission or the receipt of life support. (Funded by the Centers for Disease Control and Prevention.) [ABSTRACT FROM AUTHOR]

BACKGROUND Spread of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) B.1.1.529 (omicron) variant, which led to increased U.S. hospitalizations for coronavirus disease 2019 (Covid-19), generated concern about immune evasion and the duration of protection from vaccines in children and adolescents. Methods Using a case–control, test-negative design, we assessed vaccine effectiveness against laboratory-confirmed Covid-19 leading to hospitalization and against critical Covid-19 (i.e., leading to receipt of life support or to death). From July 1, 2021, to February 17, 2022, we enrolled case patients with Covid-19 and controls without Covid-19 at 31 hospitals in 23 states. We estimated vaccine effectiveness by comparing the odds of antecedent full vaccination (two doses of BNT162b2 messenger RNA vaccine) at least 14 days before illness among case patients and controls, according to time since vaccination for patients 12 to 18 years of age and in periods coinciding with circulation of B.1.617.2 (delta) (July 1, 2021, to December 18, 2021) and omicron (December 19, 2021, to February 17, 2022) among patients 5 to 11 and 12 to 18 years of age. RESULTS We enrolled 1185 case patients (1043 [88%] of whom were unvaccinated, 291 [25%] of whom received life support, and 14 of whom died) and 1627 controls. During the delta-predominant period, vaccine effectiveness against hospitalization for Covid-19 among adolescents 12 to 18 years of age was 93% (95% confidence interval [CI], 89 to 95) 2 to 22 weeks after vaccination and was 92% (95% CI, 80 to 97) at 23 to 44 weeks. Among adolescents 12 to 18 years of age (median interval since vaccination, 162 days) during the omicron-predominant period, vaccine effectiveness was 40% (95% CI, 9 to 60) against hospitalization for Covid-19, 79% (95% CI, 51 to 91) against critical Covid-19, and 20% (95% CI, −25 to 49) against noncritical Covid-19. During the omicron period, vaccine effectiveness against hospitalization among children 5 to 11 years of age was 68% (95% CI, 42 to 82; median interval since vaccination, 34 days). CONCLUSIONS BNT162b2 vaccination reduced the risk of omicron-associated hospitalization by two thirds among children 5 to 11 years of age. Although two doses provided lower protection against omicron-associated hospitalization than against delta-associated hospitalization among adolescents 12 to 18 years of age, vaccination prevented critical illness caused by either variant. [ABSTRACT FROM AUTHOR]

Background: Rotavirus was the leading cause of acute gastroenteritis among US children until vaccine introduction in 2006, after which, substantial declines in severe rotavirus disease occurred. We evaluated rotavirus vaccine effectiveness (VE) over 13 years (2009-2022)., Methods: We analyzed data from the New Vaccine Surveillance Network using a test-negative case-control design to estimate rotavirus VE against laboratory-confirmed rotavirus infections among children seeking care for acute gastroenteritis (≥3 diarrhea or ≥1 vomiting episodes within 24 hours) in the emergency department (ED) or hospital. Case-patients and control-patients were children whose stool specimens tested rotavirus positive or negative, respectively, by enzyme immunoassay or polymerase chain reaction assays. VE was calculated as (1-adjusted odds ratio)×100%. Adjusted odds ratios were calculated by multivariable unconditional logistic regression., Results: Among 16 188 enrolled children age 8 to 59 months, 1720 (11%) tested positive for rotavirus. Case-patients were less often vaccinated against rotavirus than control-patients (62% versus 88%). VE for receiving ≥1 dose against rotavirus-associated ED visits or hospitalization was 78% (95% confidence interval [CI] 75%-80%). Stratifying by a modified Vesikari Severity Score, VE was 59% (95% CI 49%-67%), 80% (95% CI 77%-83%), and 94% (95% CI 90%-97%) against mild, moderately severe, and very severe disease, respectively. Rotavirus vaccines conferred protection against common circulating genotypes (G1P[8], G2P[4], G3P[8], G9P[8], and G12[P8]). VE was higher in children <3 years (73% to 88%); protection decreased as age increased., Conclusions: Rotavirus vaccines remain highly effective in preventing ED visits and hospitalizations in US children., Competing Interests: CONFLICT OF INTEREST DISCLOSURES: Dr Weinberg has research support from the New York State Department of Health AIDS Institute and has received honoraria from Merck and Inhalon Biopharma; Dr Englund has research support from AstraZeneca, Merck, Pfizer, and GlaxoSmithKline and consults for AstraZeneca, GlaxoSmithKline, Pfizer, and Sanofi Pasteur; Dr Halasa has research support from Sanofi Pasteur and Quidel and an education grant from Genetech; Dr Harrison received honoraria from WebMD, and his institution received funding for research for in which he was an investigator from GSK, Merck, and Pfizer up to July 1, 2022; Dr Staat has research support from the National Institutes of Health, Merck, Pfizer, and Cepheid and has received honoraria from UpToDate; Dr Schlaudecker has research support from the National Institutes of Health and Pfizer and has received honoraria from Sanofi Pasteur; Dr Zerr received research support from Merck and honoraria from UpToDate and served as a consultant for AlloVir; and the other authors have no conflicts of interest relevant to this article to disclose., (Copyright © 2024 by the American Academy of Pediatrics.)

Competing Interests: NH declares grants or contracts from Merck (investigator-initiated) and has participated on an advisory board for CSL-Seqirus. LB declares interaction with pharmaceutical and other industrial partners, but has not received personal fees or other personal benefits; and is the founding chairman of the ReSViNET Foundation. University Medical Center Utrecht has received major funding for investigator initiated studies from AstraZeneca, Sanofi, Janssen, Pfizer, MSD, MeMed Diagnostics, and the Bill and Melinda Gates Foundation; has received major funding as part of the public–private partnership IMI-funded RESCEU and PROMISE projects with partners GlaxoSmithKline, Novavax, Janssen, AstraZeneca, Pfizer, and Sanofi; has received major funding by Julius Clinical for participating in clinical studies sponsored by AstraZeneca, Merck, and Pfizer; and has received minor funding for consultation, Data and Safety Monitoring Board membership, or invited lectures by Ablynx, Bavaria Nordic, GlaxoSmithKline, Novavax, Pfizer, Moderna, AstraZeneca, MSD, Sanofi, and Janssen.

While influenza A virus (IAV) antigenic drift has been documented globally, in experimental animal infections, and in immunocompromised hosts, positive selection has generally not been detected in acute infections. This is likely due to challenges in distinguishing selected rare mutations from sequencing error, a reliance on cross-sectional sampling, and/or the lack of formal tests of selection for individual sites. Here, we sequenced IAV populations from 346 serial, daily nasal swabs from 143 individuals collected over three influenza seasons in a household cohort. Viruses were sequenced in duplicate, and intrahost single nucleotide variants (iSNV) were identified at a 0.5% frequency threshold. Within-host populations were subject to purifying selection with >75% mutations present at <2% frequency. Children (0-5 years) had marginally higher within-host evolutionary rates than adolescents (6-18 years) and adults (>18 years, 4.4x10 -6 vs. 9.42x10 -7 and 3.45x10 -6 , p <0.001). Forty-five iSNV had evidence of parallel evolution, but were not overrepresented in HA and NA. Several increased from minority to consensus level, with strong linkage among iSNV across segments. A Wright Fisher Approximate Bayesian Computational model identified positive selection at 23/256 loci (9%) in A(H3N2) specimens and 19/176 loci (11%) in A(H1N1)pdm09 specimens, and these were infrequently found in circulation. Overall, we found that within-host IAV populations were subject to purifying selection and genetic drift, with only subtle differences across seasons, subtypes, and age strata. Positive selection was rare and inconsistently detected.

Background: Assessing variant-specific COVID-19 vaccine effectiveness (VE) and severity can inform public health risk assessments and decisions about vaccine composition. BA.2.86 and its descendants, including JN.1 (referred to collectively as "JN lineages"), emerged in late 2023 and exhibited substantial divergence from co-circulating XBB lineages., Methods: We analyzed patients hospitalized with COVID-19-like illness at 26 hospitals in 20 U.S. states admitted October 18, 2023-March 9, 2024. Using a test-negative, case-control design, we estimated effectiveness of an updated 2023-2024 (Monovalent XBB.1.5) COVID-19 vaccine dose against sequence-confirmed XBB and JN lineage hospitalization using logistic regression. Odds of severe outcomes, including intensive care unit (ICU) admission and invasive mechanical ventilation (IMV) or death, were compared for JN versus XBB lineage hospitalizations using logistic regression., Results: 585 case-patients with XBB lineages, 397 case-patients with JN lineages, and 4,580 control-patients were included. VE in the first 7-89 days after receipt of an updated dose was 54.2% (95% CI = 36.1%-67.1%) against XBB lineage hospitalization and 32.7% (95% CI = 1.9%-53.8%) against JN lineage hospitalization. Odds of ICU admission (adjusted odds ratio [aOR] 0.80; 95% CI = 0.46-1.38) and IMV or death (aOR 0.69; 95% CI = 0.34-1.40) were not significantly different among JN compared to XBB lineage hospitalizations., Conclusions: Updated 2023-2024 COVID-19 vaccination provided protection against both XBB and JN lineage hospitalization, but protection against the latter may be attenuated by immune escape. Clinical severity of JN lineage hospitalizations was not higher relative to XBB., (Published by Oxford University Press on behalf of Infectious Diseases Society of America 2024.)

Background: Influenza remains an important cause of hospitalizations in the United States. Estimating the number of influenza hospitalizations is vital for public health decision making. Combining existing surveillance systems through capture-recapture methods allows for more comprehensive burden estimations., Methods: Data from independent surveillance systems were combined using capture-recapture methods to estimate influenza hospitalization rates for children and adults in Middle Tennessee during consecutive influenza seasons from 2016-2017 through 2019-2020. The Emerging Infections Program (EIP) identified cases through surveillance of laboratory results for hospitalized children and adults. The Hospitalized Adult Influenza Vaccine Effectiveness Network (HAIVEN) and New Vaccine Surveillance Network (NVSN) recruited hospitalized patients with respiratory symptoms or fever. Population-based influenza rates and the proportion of cases detected by each surveillance system were calculated., Results: Estimated overall influenza hospitalization rates ranged from 23 influenza-related hospitalizations per 10 000 persons in 2016-2017 to 40 per 10 000 persons in 2017-2018. Adults aged ≥65 years had the highest hospitalization rates across seasons and experienced a rate of 170 hospitalizations per 10 000 persons during the 2017-2018 season. EIP consistently identified a higher proportion of influenza cases for adults and children compared with HAIVEN and NVSN, respectively., Conclusions: Current surveillance systems underestimate the influenza burden. Capture-recapture provides an alternative approach to use data from independent surveillance systems and complement population-based burden estimates., Competing Interests: Potential conflicts of interest. C. G. G. reports grants from Campbell Alliance/Syneos Health, the National Institutes of Health, the US Food and Drug Administration, the Agency for Healthcare Research and Quality, and Sanofi Pasteur, as well as consultation fees from Merck. All other authors report no 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., (© The Author(s) 2023. 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.)

Objective: Acute gastroenteritis (AGE) is the second leading cause of death in children worldwide. Objectively evaluating disease severity is critical for assessing future interventions. We used data from a large, prospective surveillance study to assess risk factors associated with severe presentation using modified Vesikari score (MVS) and Clark score (CS) of severity., Methods: From December 1, 2012 to June 30, 2016, AGE surveillance was performed for children between 15 days and 17 years old in the emergency, inpatient, and outpatient settings at Vanderbilt's Monroe Carell Jr. Children's Hospital in Nashville, TN. Stool specimens were tested for norovirus, sapovirus, rotavirus, and astrovirus. We compared demographic and clinical characteristics, along with the MVS and CS, by viral detection status and by setting., Results: Of the 6309 eligible children, 4216 (67%) were enrolled, with 3256 (77%) providing a stool specimen. The median age was 1.9 years, 52% were male, and 1387 (43%) of the stool samples were virus positive. Younger age, male sex, hospitalization, and rotavirus detection were significantly associated with higher mean MVS and CS. Non-Hispanic Black race and ethnicity was associated with a lower mean MVS and CS as compared with non-Hispanic white race and ethnicity. Prematurity and enrollment in the ED were associated with higher mean CS. The 2 scoring systems were highly correlated., Conclusions: Rotavirus continues to be associated with more severe pediatric illness compared with other viral causes of AGE. MVS and CS systems yielded comparable results and can be useful tools to assess AGE severity.

Introduction: Traditional surveillance systems may underestimate the burden caused by respiratory syncytial virus (RSV). Capture-recapture methods provide alternatives for estimating the number of RSV-related hospitalizations in a population., Methods: Capture-recapture methods were used to estimate the number of RSV-related hospitalizations in adults in Middle Tennessee from two independent hospitalization surveillance systems during consecutive respiratory seasons from 2016-2017 to 2019-2020. Data from the Hospitalized Adult Influenza Vaccine Effectiveness Network (HAIVEN) and the Emerging Infections Program (EIP) were used. Annual RSV hospitalization rates were calculated using the capture-recapture estimates weighted by hospitals' market share divided by the corresponding census population., Results: Using capture-recapture methods, the estimated overall adult hospitalization rates varied from 8.3 (95% CI: 5.9-15.4) RSV-related hospitalizations per 10,000 persons during the 2016-2017 season to 28.4 (95% CI: 18.2-59.0) hospitalizations per 10,000 persons in the 2019-2020 season. The proportion of hospitalizations that HAIVEN determined ranged from 8.7% to 36.7% of the total capture-recapture estimated hospitalization, whereas EIP detected 23.5% to 52.7% of the total capture-recapture estimated hospitalizations., Conclusion: Capture-recapture estimates showed that individual traditional surveillance systems underestimated the hospitalization burden in adults. Using capture-recapture allows for a more comprehensive estimate of RSV hospitalizations., (© 2024 The Authors. Influenza and Other Respiratory Viruses published by John Wiley & Sons Ltd.)

Background: Influenza circulation during the 2022-2023 season in the United States largely returned to pre-coronavirus disease 2019 (COVID-19)-pandemic patterns and levels. Influenza A(H3N2) viruses were detected most frequently this season, predominately clade 3C.2a1b.2a, a close antigenic match to the vaccine strain., Methods: To understand effectiveness of the 2022-2023 influenza vaccine against influenza-associated hospitalization, organ failure, and death, a multicenter sentinel surveillance network in the United States prospectively enrolled adults hospitalized with acute respiratory illness between 1 October 2022, and 28 February 2023. Using the test-negative design, vaccine effectiveness (VE) estimates against influenza-associated hospitalization, organ failures, and death were measured by comparing the odds of current-season influenza vaccination in influenza-positive case-patients and influenza-negative, SARS-CoV-2-negative control-patients., Results: A total of 3707 patients, including 714 influenza cases (33% vaccinated) and 2993 influenza- and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-negative controls (49% vaccinated) were analyzed. VE against influenza-associated hospitalization was 37% (95% confidence interval [CI]: 27%-46%) and varied by age (18-64 years: 47% [30%-60%]; ≥65 years: 28% [10%-43%]), and virus (A[H3N2]: 29% [6%-46%], A[H1N1]: 47% [23%-64%]). VE against more severe influenza-associated outcomes included: 41% (29%-50%) against influenza with hypoxemia treated with supplemental oxygen; 65% (56%-72%) against influenza with respiratory, cardiovascular, or renal failure treated with organ support; and 66% (40%-81%) against influenza with respiratory failure treated with invasive mechanical ventilation., Conclusions: During an early 2022-2023 influenza season with a well-matched influenza vaccine, vaccination was associated with reduced risk of influenza-associated hospitalization and organ failure., Competing Interests: Potential conflicts of interest. S. B. reports participating as the DSMB chair for Hamilton Ventilators, outside the submitted work. J. C. reports receiving funding from the National Institutes of Health (NIH) and Department of Defense (DoD), and a travel grant from Fisher-Paykel, outside the submitted work. S. C. reports consulting for PureTech Health in 2021–2022 and Kiniksa Pharmaceuticals in 2022, outside the submitted work. A. D. reports participating on an advisory board for ALung Technologies and being a principal investigator (PI) for the PETAL Network, outside the submitted work. C. G. G. reports consulting fees from Merck and received research support from Campbell Alliance/Syneos Health, NIH, CDC, Food and Drug Administration (FDA), and AHRQ, outside the submitted work. M. N. G. reports receiving grant funding from NIH and AHRQ for research, honorarium for giving Medicine grand rounds at Yale and Washington Healthcare, fees for DSMB for Palm trial and Regeneron trials on monoclonal antibodies, and fees for serving on scientific advisory board for Philips Healthcare on monitoring, outside the submitted work. R. G. reports consulting for Gilead Sciences, Eli Lily, GSK, Janssen, and AbbVie, being on an advisory board for Gilead Sciences, Eli Lily, GlaxoSmithKline (GSK), and AstraZeneca, speaker bureau for Pfizer and AbbVie, and gift-in-kind to institution from Gilead Sciences, outside the submitted work. N. H. reports prior grant support from Sanofi and Quidel, and current funding from Merck, outside the submitted work. A. L. reports being a consultant for Roche on a clinical trial of baloxavir, outside the submitted work. Christopher Mallow reports medical legal consulting, outside the submitted work. I. P. reports receiving grants from NHLBI, NIGMS, and Janssen Pharmaceuticals and institutional support from Regeneron, outside the submitted 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., (Published by Oxford University Press on behalf of Infectious Diseases Society of America 2023.)

Importance: On June 21, 2023, the Centers for Disease Control and Prevention recommended the first respiratory syncytial virus (RSV) vaccines for adults aged 60 years and older using shared clinical decision-making. Understanding the severity of RSV disease in adults can help guide this clinical decision-making., Objective: To describe disease severity among adults hospitalized with RSV and compare it with the severity of COVID-19 and influenza disease by vaccination status., Design, Setting, and Participants: In this cohort study, adults aged 18 years and older admitted to the hospital with acute respiratory illness and laboratory-confirmed RSV, SARS-CoV-2, or influenza infection were prospectively enrolled from 25 hospitals in 20 US states from February 1, 2022, to May 31, 2023. Clinical data during each patient's hospitalization were collected using standardized forms. Data were analyzed from August to October 2023., Exposures: RSV, SARS-CoV-2, or influenza infection., Main Outcomes and Measures: Using multivariable logistic regression, severity of RSV disease was compared with COVID-19 and influenza severity, by COVID-19 and influenza vaccination status, for a range of clinical outcomes, including the composite of invasive mechanical ventilation (IMV) and in-hospital death., Results: Of 7998 adults (median [IQR] age, 67 [54-78] years; 4047 [50.6%] female) included, 484 (6.1%) were hospitalized with RSV, 6422 (80.3%) were hospitalized with COVID-19, and 1092 (13.7%) were hospitalized with influenza. Among patients with RSV, 58 (12.0%) experienced IMV or death, compared with 201 of 1422 unvaccinated patients with COVID-19 (14.1%) and 458 of 5000 vaccinated patients with COVID-19 (9.2%), as well as 72 of 699 unvaccinated patients with influenza (10.3%) and 20 of 393 vaccinated patients with influenza (5.1%). In adjusted analyses, the odds of IMV or in-hospital death were not significantly different among patients hospitalized with RSV and unvaccinated patients hospitalized with COVID-19 (adjusted odds ratio [aOR], 0.82; 95% CI, 0.59-1.13; P = .22) or influenza (aOR, 1.20; 95% CI, 0.82-1.76; P = .35); however, the odds of IMV or death were significantly higher among patients hospitalized with RSV compared with vaccinated patients hospitalized with COVID-19 (aOR, 1.38; 95% CI, 1.02-1.86; P = .03) or influenza disease (aOR, 2.81; 95% CI, 1.62-4.86; P < .001)., Conclusions and Relevance: Among adults hospitalized in this US cohort during the 16 months before the first RSV vaccine recommendations, RSV disease was less common but similar in severity compared with COVID-19 or influenza disease among unvaccinated patients and more severe than COVID-19 or influenza disease among vaccinated patients for the most serious outcomes of IMV or death.

Background: Prolonged SARS-CoV-2 infections in people who are immunocompromised might predict or source the emergence of highly mutated variants. The types of immunosuppression placing patients at highest risk for prolonged infection have not been systematically investigated. We aimed to assess risk factors for prolonged SARS-CoV-2 infection and associated intrahost evolution., Methods: In this multicentre, prospective analysis, participants were enrolled at five US medical centres. Eligible patients were aged 18 years or older, were SARS-CoV-2-positive in the previous 14 days, and had a moderately or severely immunocompromising condition or treatment. Nasal specimens were tested by real-time RT-PCR every 2-4 weeks until negative in consecutive specimens. Positive specimens underwent viral culture and whole genome sequencing. A Cox proportional hazards model was used to assess factors associated with duration of infection., Findings: From April 11, 2022, to Oct 1, 2022, 156 patients began the enrolment process, of whom 150 were enrolled and included in the analyses. Participants had B-cell malignancy or anti-B-cell therapy (n=18), solid organ transplantation or haematopoietic stem-cell transplantation (HSCT; n=59), AIDS (n=5), non-B-cell malignancy (n=23), and autoimmune or autoinflammatory conditions (n=45). 38 (25%) participants were real-time RT-PCR-positive and 12 (8%) were culture-positive 21 days or longer after initial SARS-CoV-2 detection or illness onset. Compared with the group with autoimmune or autoinflammatory conditions, patients with B-cell dysfunction (adjusted hazard ratio 0·32 [95% CI 0·15-0·64]), solid organ transplantation or HSCT (0·60 [0·38-0·94]), and AIDS (0·28 [0·08-1·00]) had longer duration of infection, defined as time to last positive real-time RT-PCR test. There was no significant difference in the non-B-cell malignancy group (0·58 [0·31-1·09]). Consensus de novo spike mutations were identified in five individuals who were real-time RT-PCR-positive longer than 56 days; 14 (61%) of 23 were in the receptor-binding domain. Mutations shared by multiple individuals were rare (<5%) in global circulation., Interpretation: In this cohort, prolonged replication-competent omicron SARS-CoV-2 infections were uncommon. Within-host evolutionary rates were similar across patients, but individuals with infections lasting longer than 56 days accumulated spike mutations, which were distinct from those seen globally. Populations at high risk should be targeted for repeated testing and treatment and monitored for the emergence of antiviral resistance., Funding: US Centers for Disease Control and Prevention., Competing Interests: Declaration of interests JDC reports receiving grants from the National Institutes of Health (NIH) and the Department of Defense, outside the submitted work. CGG reports grants from NIH, the Centers for Disease Control and Prevention (CDC), the Agency for Healthcare Research and Quality, the US Food and Drug Administration, and Campbell Alliance/Syneos Health, and consulting fees and participating on a data safety monitoring board for Merck, outside the submitted work. AEF reports a K08 award from NIH and participating on the Hennepin Health Research Institute Board of Directors, outside the submitted work. NH reports grants from Sanofi, Quidel, and Merck, outside the submitted work. ASL reports receiving grants from CDC, National Institute of Allergy and Infectious Diseases, Burroughs Wellcome Fund, and Flu Lab, and consulting fees from Roche, outside the submitted work. ETM reports receiving a grant from Merck, outside the submitted work. All other authors declare no competing interests., (Copyright © 2023 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

Background and Objectives: In June 2022, the mRNA COVID-19 vaccination was recommended for young children. We examined clinical characteristics and factors associated with vaccination status among vaccine-eligible young children hospitalized for acute COVID-19., Methods: We enrolled inpatients 8 months to <5 years of age with acute community-acquired COVID-19 across 28 US pediatric hospitals from September 20, 2022 to May 31, 2023. We assessed demographic and clinical factors, including the highest level of respiratory support, and vaccination status defined as unvaccinated, incomplete, or complete primary series [at least 2 (Moderna) or 3 (Pfizer-BioNTech) mRNA vaccine doses ≥14 days before hospitalization]., Results: Among 597 children, 174 (29.1%) patients were admitted to the intensive care unit and 75 (12.6%) had a life-threatening illness, including 51 (8.5%) requiring invasive mechanical ventilation. Children with underlying respiratory and neurologic/neuromuscular conditions more frequently received higher respiratory support. Only 4.5% of children hospitalized for COVID-19 (n = 27) had completed their primary COVID-19 vaccination series and 7.0% (n = 42) of children initiated but did not complete their primary series. Among 528 unvaccinated children, nearly half (n = 251) were previously healthy, 3 of them required extracorporeal membrane oxygenation for acute COVID-19 and 1 died., Conclusions: Most young children hospitalized for acute COVID-19, including most children admitted to the intensive care unit and with life-threatening illness, had not initiated COVID-19 vaccination despite being eligible. Nearly half of these children had no underlying conditions. Of the small percentage of children who initiated a COVID-19 primary series, most had not completed it before hospitalization., Competing Interests: The authors have no conflicts of interest to disclose., (Copyright © 2023 Wolters Kluwer Health, Inc. All rights reserved.)

Competing Interests: All authors have completed and submitted the International Committee of Medical Journal Editors form for disclosure of potential conflicts of interest. No potential conflicts of interest were disclosed.

Background: The ongoing COVID-19 pandemic has led to hundreds of millions of infections worldwide. Although differences in COVID-19 hospitalization rates between males and females have been described, many infections in the general population have been mild, and the severity of symptoms during the course of COVID-19 in non-hospitalized males and females is not well understood., Methods: We conducted a case-ascertained study to examine household transmission of SARS-CoV-2 infections in Nashville, Tennessee, between April 2020 and April 2021. Among enrolled ambulatory adult participants with laboratory-confirmed SARS-CoV-2 infections, we assessed the presence and severity of symptoms (total, systemic, and respiratory) daily using a symptoms severity questionnaire, from illness onset and throughout the 2-week follow-up period. We compared the mean daily symptom severity scores (0-3: none, mild, moderate, and severe) and change in symptoms between males and females using a multivariable linear mixed effects regression model., Results: The analysis included 223 enrolled adults with SARS-CoV-2 infection (58% females, mostly white, non-Hispanic) from 146 households with 2917 total daily symptom reports. The overall mean severity of total symptoms reported over the illness period was 1.04 and 0.90 for females and males, respectively. Mean systemic and respiratory scores were higher for females than for males ( p  < 0.001). In multivariable analyses, females reported more severe total and systemic symptoms during the illness period compared with males. However, no significant differences in reported respiratory symptoms were observed., Conclusions: Our findings indicate that among ambulatory adults with SARS-CoV-2 infections, females reported slightly higher symptom severity during their illness compared with males., Competing Interests: C.G.G. reports grants from Syneos Health, the National Institutes of Health, the Food and Drug Administration, the Agency for Health Care Research and Quality, and consultation fees from Merck. The other authors have no potential conflicts of interest to report., (© 2023 The Authors. Influenza and Other Respiratory Viruses published by John Wiley & Sons Ltd.)

On June 21, 2023, CDC's Advisory Committee on Immunization Practices recommended respiratory syncytial virus (RSV) vaccination for adults aged ≥60 years, offered to individual adults using shared clinical decision-making. Informed use of these vaccines requires an understanding of RSV disease severity. To characterize RSV-associated severity, 5,784 adults aged ≥60 years hospitalized with acute respiratory illness and laboratory-confirmed RSV, SARS-CoV-2, or influenza infection were prospectively enrolled from 25 hospitals in 20 U.S. states during February 1, 2022-May 31, 2023. Multivariable logistic regression was used to compare RSV disease severity with COVID-19 and influenza severity on the basis of the following outcomes: 1) standard flow (<30 L/minute) oxygen therapy, 2) high-flow nasal cannula (HFNC) or noninvasive ventilation (NIV), 3) intensive care unit (ICU) admission, and 4) invasive mechanical ventilation (IMV) or death. Overall, 304 (5.3%) enrolled adults were hospitalized with RSV, 4,734 (81.8%) with COVID-19 and 746 (12.9%) with influenza. Patients hospitalized with RSV were more likely to receive standard flow oxygen, HFNC or NIV, and ICU admission than were those hospitalized with COVID-19 or influenza. Patients hospitalized with RSV were more likely to receive IMV or die compared with patients hospitalized with influenza (adjusted odds ratio = 2.08; 95% CI = 1.33-3.26). Among hospitalized older adults, RSV was less common, but was associated with more severe disease than COVID-19 or influenza. High disease severity in older adults hospitalized with RSV is important to consider in shared clinical decision-making regarding RSV vaccination., Competing Interests: All authors have completed and submitted the International Committee of Medical Journal Editors form for disclosure of potential conflicts of interest. Samuel M. Brown reports that ReddyPort pays royalties on his invention of an airway device, outside the submitted work. Jonathan D. Casey reports a travel grant from Fisher and Paykel, outside the submitted work. Steven Y. Chang reports consulting fees from PureTech Health and Kiniksa Pharmaceuticals and participation as a data safety monitoring board member for a study at University of California, Los Angeles outside the submitted work. James D. Chappell reports participating as a coinvestigator for a Merck investigator studies program, where he supported surveillance of respiratory syncytial virus infection among hospitalized children in Jordan, outside the submitted work. Manjusha Gaglani reports grants from Abt Associates and Westat, having served as cochair of the Infectious Diseases and Immunization Committee for the Texas Pediatric Society (TPS), and receiving an honorarium for serving as a TPS Project Firstline webinar speaker panelist for Respiratory Virus Review: Clinical Considerations and IPC Guidance, outside the submitted work. Adit A. Ginde reports receiving grants from the National Institutes of Health (NIH), U.S. Department of Defense, AbbVie, and Faron Pharmaceuticals outside the submitted work. Michelle N. Gong reports a grant from NIH outside the submitted work. Carlos G. Grijalva reports grants from NIH, the Agency for Healthcare Research and Quality, Food and Drug Administration, and Syneos Health, and receipt of compensation for participation in an advisory board for Merck outside the submitted work. Natasha Halasa reports receiving grants from Sanofi, Merck, and Quidel outside the submitted work. Akram Khan reports receiving grants from United Therapeutics, Johnson & Johnson, 4D Medical, Eli Lily, Dompe Pharmaceuticals, and GSK outside the submitted work. Adam S. Lauring reports receiving grants from FluLab, NIH/National Institute of Allergy and Infectious Diseases, and Burroughs Wellcome Fund and fees from Sanofi and Roche for consulting on oseltamivir and baloxavir respectively, outside the submitted work. Emily T. Martin reports a grant from Merck outside the submitted work. Christopher Mallow reports medical legal consulting outside the submitted work. Ithan D. Peltan reports grants from NIH and Janssen Pharmaceuticals and institutional support from Asahi Kasei Pharma and Regeneron outside the submitted work. Mayur Ramesh reports participating in a nonbranded speaker program supported by AstraZeneca and serving on an advisory board for Moderna outside the submitted work. No other potential conflicts of interest were disclosed.

Importance: The COVID-19 pandemic has been associated with a transient decrease in bronchiolitis hospitalizations compared with prepandemic patterns, but current effects remain unknown., Objective: To analyze changes in patterns of bronchiolitis admissions at US children's hospitals during the 2020-2023 bronchiolitis seasons compared with the 2010-2019 seasons., Design, Setting, and Participants: This retrospective cross-sectional study used data from 41 US children's hospitals in the Pediatric Health Information System database. Bronchiolitis has winter-predominant seasonality, so hospitalizations were grouped according to bronchiolitis season (from July through June). This study included all patients aged younger than 2 years admitted with a diagnosis of bronchiolitis between July 1, 2010, and June 30, 2023. Bronchiolitis seasons from July through June between 2010-2011 and 2019-2020 were classified as the prepandemic era, and seasons between 2020-2021 and 2022-2023 were classified as the pandemic era. Data analysis was performed from July 1, 2010, through June 30, 2023., Exposures: Admission date., Main Outcomes and Measures: The primary outcome was number of hospitalizations for bronchiolitis by season and month. Monthly admission counts from the prepandemic era were transformed into time series and used to train seasonal ensemble forecasting models. Forecasts were compared to monthly admissions during the pandemic era., Results: In this study, there were 400 801 bronchiolitis admissions among 349 609 patients between July 1, 2010, and June 30, 2023. The median patient age was 6 (IQR, 2-12) months; 58.7% were boys and 43.7% were White. Hospitalizations increased gradually during the prepandemic era (median, 29 309 [IQR, 26 196-34 157]), decreased 69.2% (n = 9030) in the 2020-2021 season, and increased 75.3% (n = 51 397) in the 2022-2023 season. Patients in the pandemic era were older than those in the prepandemic era (median, 7 [IQR, 3-14] vs 6 [2-12] months; P < .001). Intensive care unit (ICU) admissions increased from 32.2% (96 245 of 298 535) in the prepandemic era to 36.7% (37 516 of 102 266) in the pandemic era (P < .001). The seasonality of bronchiolitis admissions changed during the pandemic era. Admissions peaked in August 2021 (actual 5036 vs 943 [95% CI, 0-2491] forecasted) and November 2022 (actual 10 120 vs 5268 [95% CI, 3425-7419] forecasted). These findings were unchanged in sensitivity analyses excluding children with complex chronic conditions and excluding repeat admissions. In a sensitivity analysis including all viral lower respiratory tract infections in children aged younger than 5 years, there were 66 767 admissions in 2022-2023 vs 35 623 (31 301-41 002) in the prepandemic era, with the largest increase in children aged 24 to 59 months., Conclusions and Relevance: The findings of this cross-sectional study suggest that bronchiolitis hospitalizations decreased transiently and then increased markedly during the COVID-19 pandemic era. Patients admitted during the pandemic era were older and were more likely to be admitted to an ICU. These findings suggest that bronchiolitis seasonality has not yet returned to prepandemic patterns, and US hospitals should prepare for the possibility of atypical timing again in 2023.

Background: Adjunctive diagnostic studies (aDS) are recommended to identify occult dissemination in patients with candidemia. Patterns of evaluation with aDS across pediatric settings are unknown., Methods: Candidemia episodes were included in a secondary analysis of a multicenter comparative effectiveness study that prospectively enrolled participants age 120 days to 17 years with invasive candidiasis (predominantly candidemia) from 2014 to 2017. Ophthalmologic examination (OE), abdominal imaging (AbdImg), echocardiogram, neuroimaging, and lumbar puncture (LP) were performed per clinician discretion. Adjunctive diagnostic studies performance and positive results were determined per episode, within 30 days from candidemia onset. Associations of aDS performance with episode characteristics were evaluated via mixed-effects logistic regression., Results: In 662 pediatric candidemia episodes, 490 (74%) underwent AbdImg, 450 (68%) OE, 426 (64%) echocardiogram, 160 (24%) neuroimaging, and 76 (11%) LP; performance of each aDS per episode varied across sites up to 16-fold. Longer durations of candidemia were associated with undergoing OE, AbdImg, and echocardiogram. Immunocompromised status (58% of episodes) was associated with undergoing AbdImg (adjusted odds ratio [aOR] 2.38; 95% confidence intervals [95% CI] 1.51-3.74). Intensive care at candidemia onset (30% of episodes) was associated with undergoing echocardiogram (aOR 2.42; 95% CI 1.51-3.88). Among evaluated episodes, positive OE was reported in 15 (3%), AbdImg in 30 (6%), echocardiogram in 14 (3%), neuroimaging in 9 (6%), and LP in 3 (4%)., Conclusions: Our findings show heterogeneity in practice, with some clinicians performing aDS selectively, potentially influenced by clinical factors. The low frequency of positive results suggests that targeted application of aDS is warranted., (© 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: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) genomic and subgenomic RNA levels are frequently used as a correlate of infectiousness. The impact of host factors and SARS-CoV-2 lineage on RNA viral load is unclear., Methods: Total nucleocapsid (N) and subgenomic N (sgN) RNA levels were measured by quantitative reverse transcription polymerase chain reaction (RT-qPCR) in specimens from 3204 individuals hospitalized with coronavirus disease 2019 (COVID-19) at 21 hospitals. RT-qPCR cycle threshold (Ct) values were used to estimate RNA viral load. The impact of time of sampling, SARS-CoV-2 variant, age, comorbidities, vaccination, and immune status on N and sgN Ct values were evaluated using multiple linear regression., Results: Mean Ct values at presentation for N were 24.14 (SD 4.53) for non-variants of concern, 25.15 (SD 4.33) for Alpha, 25.31 (SD 4.50) for Delta, and 26.26 (SD 4.42) for Omicron. N and sgN RNA levels varied with time since symptom onset and infecting variant but not with age, comorbidity, immune status, or vaccination. When normalized to total N RNA, sgN levels were similar across all variants., Conclusions: RNA viral loads were similar among hospitalized adults, irrespective of infecting variant and known risk factors for severe COVID-19. Total N and subgenomic RNA N viral loads were highly correlated, suggesting that subgenomic RNA measurements add little information for the purposes of estimating infectivity., Competing Interests: Potential conflicts of interest. J. Ca. reports grants from National Institutes of Health (NIH) and Department of Defense (DoD), outside the submitted work. J. Ch. reports grants from the NIH, DoD, and Dolly Parton COVID-19 Research Fund, outside the submitted work. D. D. reports a grant from NIH, outside the submitted work. A. D. reports grants from the NIH and National Heart, Lung, and Blood Institute (NHLBI) for the ACTIV platform and PETAL network, respectively; and consulting fees for Alung Technologies, outside the submitted work. M. E. reports grants from NIH and Regeneron; personal funds for speaking at the ASPEN conference for Abbott Labs; and payment for testimony from Medical Legal Expert Witness, outside the submitted work. A. F. reports grants from NIH, outside the submitted work. M. G. reports grants from CDC, CDC-Abt Associates, and CDC-Westat; and served as cochair of the Infectious Diseases and Immunization Committee for the Texas Pediatric Society, outside the submitted work. K. G. reports grants from NIH and DoD; and support for MHSRS 2022 travel from the DoD, outside the submitted work. A. G. reports grants from NIH, DoD, AbbVie, and Faron Pharmaceuticals, outside the submitted work. M. N. G. reports grants from NHLBI, CDC, and Agency for Healthcare Research and Quality; speaking at medicine grand rounds at New York Medical College; travel support for the American Thoracic Society (ATS) executive meeting and serving as ATS Chair Critical Care Assembly; data and safety monitoring board (DSMB) membership fees from Regeneron; and participating on the scientific advisory panel for Endpoint, outside the submitted work. C. G. reports grants from NIH, CDC, AHRQ, FDA, and Campbell Alliance/Syneos Health; and consulting fees from and participating on a DSMB for Merck, outside the submitted work. D. H. reports grants from NHLBI, outside the submitted work. N. H. reports grants from Sandofi and Quidel; and a Genentech educational grant to give a lecture, outside the submitted work. A. K. reports grants from United Therapeutics, Johnson & Johnson, 4D Medical, Eli Lily, Dompe Pharmaceuticals, and GlaxoSmithKline; and serves on the guidelines committee for Chest, outside the submitted work. A. L. reports grants from CDC, National Institute of Allergy and Infectious Diseases, and Burroughs Wellcome Fund; and consulting fees from Sanofi and Roche for consulting on oseltamivir and baloxavir, respectively, outside the submitted work. E. M. reports grants from Flu Lab, Merck, and NIH outside the submitted work. T. M. reports a grant from CDC; a one-time payment for participating as a virtual webinar panelist for Clinical Updates in Heart Failure; and being a Practice Management Committee member for Society of Hospital Medicine, outside the submitted work. I. D. P. reports grants from NIH and Janssen Pharmaceuticals; and institutional support from Asahi Kasei Pharma and Regeneron, outside the submitted work. W. B. S. reports grants and support for meetings/travel from the NIH/NHLBI, outside the submitted work. J. W. reports payment for the American College of Emergency Physicians speaker honorarium and participating on the American Board of Internal Medicine Critical Care Exam Committee, outside the submitted 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) 2023. 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.)

Importance: Respiratory syncytial virus (RSV) is the leading cause of lower respiratory tract infections (LRTIs) and infant hospitalization worldwide., Objective: To evaluate the characteristics and outcomes of RSV-related critical illness in US infants during peak 2022 RSV transmission., Design, Setting, and Participants: This cross-sectional study used a public health prospective surveillance registry in 39 pediatric hospitals across 27 US states. Participants were infants admitted for 24 or more hours between October 17 and December 16, 2022, to a unit providing intensive care due to laboratory-confirmed RSV infection., Exposure: Respiratory syncytial virus., Main Outcomes and Measures: Data were captured on demographics, clinical characteristics, signs and symptoms, laboratory values, severity measures, and clinical outcomes, including receipt of noninvasive respiratory support, invasive mechanical ventilation, vasopressors or extracorporeal membrane oxygenation, and death. Mixed-effects multivariable log-binomial regression models were used to assess associations between intubation status and demographic factors, gestational age, and underlying conditions, including hospital as a random effect to account for between-site heterogeneity., Results: The first 15 to 20 consecutive eligible infants from each site were included for a target sample size of 600. Among the 600 infants, the median (IQR) age was 2.6 (1.4-6.0) months; 361 (60.2%) were male, 169 (28.9%) were born prematurely, and 487 (81.2%) had no underlying medical conditions. Primary reasons for admission included LRTI (594 infants [99.0%]) and apnea or bradycardia (77 infants [12.8%]). Overall, 143 infants (23.8%) received invasive mechanical ventilation (median [IQR], 6.0 [4.0-10.0] days). The highest level of respiratory support for nonintubated infants was high-flow nasal cannula (243 infants [40.5%]), followed by bilevel positive airway pressure (150 infants [25.0%]) and continuous positive airway pressure (52 infants [8.7%]). Infants younger than 3 months, those born prematurely (gestational age <37 weeks), or those publicly insured were at higher risk for intubation. Four infants (0.7%) received extracorporeal membrane oxygenation, and 2 died. The median (IQR) length of hospitalization for survivors was 5 (4-10) days., Conclusions and Relevance: In this cross-sectional study, most US infants who required intensive care for RSV LRTIs were young, healthy, and born at term. These findings highlight the need for RSV preventive interventions targeting all infants to reduce the burden of severe RSV illness.

Background: The mechanism for anaphylaxis following mRNA COVID-19 vaccination has been widely debated; understanding this serious adverse event is important for future vaccines of similar design. A mechanism proposed is type I hypersensitivity (i.e., IgE-mediated mast cell degranulation) to polyethylene glycol (PEG). Using an assay that, uniquely, had been previously assessed in patients with anaphylaxis to PEG, our objective was to compare anti-PEG IgE in serum from mRNA COVID-19 vaccine anaphylaxis case-patients and persons vaccinated without allergic reactions. Secondarily, we compared anti-PEG IgG and IgM to assess alternative mechanisms., Methods: Selected anaphylaxis case-patients reported to U.S. Vaccine Adverse Event Reporting System December 14, 2020-March 25, 2021 were invited to provide a serum sample. mRNA COVID-19 vaccine study participants with residual serum and no allergic reaction post-vaccination ("controls") were frequency matched to cases 3:1 on vaccine and dose number, sex and 10-year age category. Anti-PEG IgE was measured using a dual cytometric bead assay (DCBA). Anti-PEG IgG and IgM were measured using two different assays: DCBA and a PEGylated-polystyrene bead assay. Laboratorians were blinded to case/control status., Results: All 20 case-patients were women; 17 had anaphylaxis after dose 1, 3 after dose 2. Thirteen (65 %) were hospitalized and 7 (35 %) were intubated. Time from vaccination to serum collection was longer for case-patients vs controls (post-dose 1: median 105 vs 21 days). Among Moderna recipients, anti-PEG IgE was detected in 1 of 10 (10 %) case-patients vs 8 of 30 (27 %) controls (p = 0.40); among Pfizer-BioNTech recipients, it was detected in 0 of 10 case-patients (0 %) vs 1 of 30 (3 %) controls (p >n 0.99). Anti-PEG IgE quantitative signals followed this same pattern. Neither anti-PEG IgG nor IgM was associated with case status with both assay formats., Conclusion: Our results support that anti-PEG IgE is not a predominant mechanism for anaphylaxis post-mRNA COVID-19 vaccination., Competing Interests: Declaration of Competing Interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Mary A Staat reports a relationship with Pfizer that includes: funding grants. Mary A Staat reports a relationship with Merck & Co Inc that includes: funding grants. Mary A Staat reports a relationship with UpToDate that includes: consulting or advisory. Donna S. Hummell reports a relationship with Merck & Co Inc that includes: consulting or advisory. Kathryn M. Edwards reports a relationship with Bionet that includes: consulting or advisory. Kathryn M. Edwards reports a relationship with IBM that includes: consulting or advisory. Kathryn M. Edwards reports a relationship with Member Data that includes: consulting or advisory. Kathryn M. Edwards reports a relationship with Sanofi, X-4 Pharma, Seqirus, Moderna, Pfizer, Merck, Roache, Novavax, Brighton Collaboration that includes: consulting or advisory. UpToDate fees for Mary A. Stadt were classified as royalties that are unrelated to this work. Consultative work by Kathryn M. Edwards for X-4 Pharma, Seqirus, Moderna, Pfizer, Merck, Roche, Novavax, Brighton Collaboration was serving on Safety and Monitoring Boards. Consultative work by Donna S. Hummel for Merck was for eDMC monitoring for clinical trial., (Published by Elsevier Ltd.)

Background: In a 2020 pilot case-control study using medical records, we reported that non-Hispanic Black children were more likely to develop multisystem inflammatory syndrome in children (MIS-C) after adjustment for sociodemographic factors and underlying medical conditions. Using structured interviews, we investigated patient, household, and community factors underlying MIS-C likelihood., Methods: MIS-C case patients hospitalized in 2021 across 14 US pediatric hospitals were matched by age and site to outpatient controls testing positive for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) within 3 months of the admission date. Caregiver interviews queried race/ethnicity, medical history, and household and potential community exposures 1 month before MIS-C hospitalization (case-patients) or after SARS-CoV-2 infection (controls). We calculated adjusted odds ratios (aOR) using mixed-effects multivariable logistic regression., Results: Among 275 case patients and 496 controls, race/ethnicity, social vulnerability and patient or family history of autoimmune/rheumatologic disease were not associated with MIS-C. In previously healthy children, MIS-C was associated with a history of hospitalization for an infection [aOR: 4.8; 95% confidence interval (CI): 2.1-11.0]. Household crowding (aOR: 1.7; 95% CI: 1.2-2.6), large event attendance (aOR: 1.7; 95% CI: 1.3-2.1), school attendance with limited masking (aOR: 2.6; 95% CI: 1.1-6.6), public transit use (aOR: 1.8; 95% CI: 1.4-2.4) and co-resident testing positive for SARS-CoV-2 (aOR: 2.2; 95% CI: 1.3-3.7) were associated with increased MIS-C likelihood, with risk increasing with the number of these factors., Conclusions: From caregiver interviews, we clarify household and community exposures associated with MIS-C; however, we did not confirm prior associations between sociodemographic factors and MIS-C., (Copyright © 2023 Wolters Kluwer Health, Inc. All rights reserved.)

As of April 2023, the COVID-19 pandemic has resulted in 1.1 million deaths in the United States, with approximately 75% of deaths occurring among adults aged ≥65 years (1). Data on the durability of protection provided by monovalent mRNA COVID-19 vaccination against critical outcomes of COVID-19 are limited beyond the Omicron BA.1 lineage period (December 26, 2021-March 26, 2022). In this case-control analysis, the effectiveness of 2-4 monovalent mRNA COVID-19 vaccine doses was evaluated against COVID-19-associated invasive mechanical ventilation (IMV) and in-hospital death among immunocompetent adults aged ≥18 years during February 1, 2022-January 31, 2023. Vaccine effectiveness (VE) against IMV and in-hospital death was 62% among adults aged ≥18 years and 69% among those aged ≥65 years. When stratified by time since last dose, VE was 76% at 7-179 days, 54% at 180-364 days, and 56% at ≥365 days. Monovalent mRNA COVID-19 vaccination provided substantial, durable protection against IMV and in-hospital death among adults during the Omicron variant period. All adults should remain up to date with recommended COVID-19 vaccination to prevent critical COVID-19-associated outcomes., Competing Interests: All authors have completed and submitted the International Committee of Medical Journal Editors form for disclosure of potential conflicts of interest. Jonathan D. Casey reports grants from the National Institutes of Health (NIH) and the U.S. Department of Defense (DoD), and a travel grant from Fisher and Paykel, outside the submitted work. Steven Y. Chang reports consulting fees from PureTech Health and Kiniksa Pharmaceuticals, and participation as a Data Safety Monitoring Board (DSMB) member for a study at UCLA, outside the submitted work. Abhijit Duggal reports grants from NIH/National Heart, Lung, and Blood Institute (NHLBI), and consulting fees from Alung Technologies, outside the submitted work. David J. Douin reports a grant from NIH/National Institute of General Medical Sciences, outside the submitted work. Matthew C. Exline reports grants from NIH and Regeneron, honoria for speaking at the American Society for Parenteral and Enteral Nutrition conference from Abbott Labs, and payment for testimony as a medical legal expert witness, outside the submitted work. D. Clark Files reports receiving a grant from NIH and participating on the Medpace DSMB, outside the submitted work. Manjusha Gaglani reports having served as co-chair of the Infectious Diseases and Immunization Committee for the Texas Pediatric Society, outside the submitted work. Kevin W. Gibbs reports grants from NIH and DoD, as well as support for travel to the 2022 Military Health System Research Symposium from DoD, outside the submitted work. Adit A. Ginde reports receiving grants from NIH, DoD, AbbVie, and Faron Pharmaceuticals, outside the submitted work. Michelle N. Gong reports grants from NHLBI, the Agency for Healthcare Research and Quality (AHRQ), speaking at medicine grand rounds at Yale and Westchester Medical College, travel support from the American Thoracic Society (ATS) and serving on the ATS board, DSMB membership fees from Regeneron and the Replenish Trial, and participating on the scientific advisory panel for Endpoint, outside the submitted work. Carlos G. Grijalva reports grants from NIH, AHRQ, the Food and Drug Administration (FDA), Campbell Alliance/Syneos Health; receipt of consulting fees from and participation on a DSMB for Merck, outside the submitted work. David N. Hager reports receiving grants from NIH, outside the submitted work. Natasha Halasa reports receiving grants from Sanofi and Quidel, outside the submitted work. Akram Khan reports receiving grants from United Therapeutics, Johnson & Johnson, 4D Medical, Eli Lily, Dompe Pharmaceuticals, and GlaxoSmithKline; and serves on the guidelines committee for Chest, outside the submitted work. Adam S. Lauring reports receiving grants from FluLab, NIH/National Institute of Allergy and Infectious Diseases, and Burroughs Wellcome Fund, and consulting fees from Sanofi and Roche for consulting on oseltamivir and baloxavir respectively, outside the submitted work. Emily T. Martin reports grants from Merck and NIH, outside the submitted work. Tresa McNeal reports receiving a one-time payment for participating as a virtual webinar panelist for Clinical Updates in Heart Failure, and being a Practice Management Committee member for Society of Hospital Medicine, outside the submitted work. Arnold S. Monto reports a grant from NIH/NIAID, support for travel from the International Society for Influenza and other Respiratory Diseases, and participation on an advisory board for FDA, outside the submitted work. Ithan D. Peltan reports grants from NIH and Janssen Pharmaceuticals and institutional support from Asahi Kasei Pharma and Regeneron, outside the submitted work. Jay S. Steingrub reports a grant from NHLBI, outside the submitted work. Jennifer G. Wilson reports grants from NHLBI, outside the submitted work. No other potential conflicts of interest were disclosed.

Background: Despite the disproportionate morbidity and mortality experienced by American Indian and Alaska Native (AI/AN) persons during the coronavirus disease 2019 (COVID-19) pandemic, few studies have reported vaccine effectiveness (VE) estimates among these communities., Methods: We conducted a test-negative case-control analysis among AI/AN persons aged ≥12 years presenting for care from January 1, 2021, through November 30, 2021, to evaluate the effectiveness of mRNA COVID-19 vaccines against COVID-19-associated outpatient visits and hospitalizations. Cases and controls were patients with ≥1 symptom consistent with COVID-19-like illness; cases were defined as those test-positive for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), and controls were defined as those test-negative for SARS-CoV-2. We used unconditional multivariable logistic regression to estimate VE, defined as 1 minus the adjusted odds ratio for vaccination among cases vs controls., Results: The analysis included 207 cases and 267 test-negative controls. Forty-four percent of cases and 78% of controls received 2 doses of either BNT162b2 or mRNA-1273 vaccine. VE point estimates for 2 doses of mRNA vaccine were higher for hospitalized participants (94.6%; 95% CI, 88.0-97.6) than outpatient participants (86.5%; 95% CI, 63.0-95.0), but confidence intervals overlapped., Conclusions: Among AI/AN persons, mRNA COVID-19 vaccines were highly effective in preventing COVID-associated outpatient visits and hospitalizations. Maintaining high vaccine coverage, including booster doses, will reduce the burden of disease in this population., Competing Interests: Potential conflicts of interest. C.S.L. reports employment as an Independent Contractor at Pfizer, Inc., from April 8, 2022, through June 8, 2022. N.H. reports research funding to her institution from Sanofi and Quidel; she also reports receipt of an educational grant from Genetech, Inc. L.L.H. reports research funding to her institution from Pfizer, Inc., and Merck & Co. H.M. reports funding to her institution from the National Institutes of Health (NIH), CDC, Maryland Department of Health, Johns Hopkins University, and National Institute of Allergy and Infectious Diseases; she reports research contracts with Bio-Rad, DiaSorin, and Hologic. C.G.S. reports research funding to her institution from the Department of Defense and NIH. All other authors report no potential conflicts., (© The Author(s) 2023. Published by Oxford University Press on behalf of Infectious Diseases Society of America.)

Background: The COVID-19 pandemic was associated with historically low influenza circulation during the 2020-2021 season, followed by an increase in influenza circulation during the 2021-2022 US season. The 2a.2 subgroup of the influenza A(H3N2) 3C.2a1b subclade that predominated was antigenically different from the vaccine strain., Methods: To understand the effectiveness of the 2021-2022 vaccine against hospitalized influenza illness, a multistate sentinel surveillance network enrolled adults aged ≥18 years hospitalized with acute respiratory illness and tested for influenza by a molecular assay. Using the test-negative design, vaccine effectiveness (VE) was measured by comparing the odds of current-season influenza vaccination in influenza-positive case-patients and influenza-negative, SARS-CoV-2-negative controls, adjusting for confounders. A separate analysis was performed to illustrate bias introduced by including SARS-CoV-2-positive controls., Results: A total of 2334 patients, including 295 influenza cases (47% vaccinated), 1175 influenza- and SARS-CoV-2-negative controls (53% vaccinated), and 864 influenza-negative and SARS-CoV-2-positive controls (49% vaccinated), were analyzed. Influenza VE was 26% (95% CI: -14% to 52%) among adults aged 18-64 years, -3% (-54% to 31%) among adults aged ≥65 years, and 50% (15-71%) among adults aged 18-64 years without immunocompromising conditions. Estimated VE decreased with inclusion of SARS-CoV-2-positive controls., Conclusions: During a season where influenza A(H3N2) was antigenically different from the vaccine virus, vaccination was associated with a reduced risk of influenza hospitalization in younger immunocompetent adults. However, vaccination did not provide protection in adults ≥65 years of age. Improvements in vaccines, antivirals, and prevention strategies are warranted., Competing Interests: Potential conflicts of interest. M. G. reports grants from the Centers for Disease Control and Prevention (CDC), CDC-Abt Associates, CDC-Westat, and Janssen, and a leadership position as co-chair of the Infection Diseases and Immunizations Committee. J. S. S. reports a grant from the National Institutes of Health (NIH). A. D. reports grants from the NIH-PETAL Network, ACTIV-3b, ACTIV-4d, and GRAIL and consulting fees from Alung Technologies. M. E. P. reports a grant from the US Department of Defense and support for speaking at the 2022 North American Congress of Clinical Toxicology. I. D. P. reports grants from NIH, Janssen, Regeneron, and Asahi Kasei Pharma. D. N. H. reports grants from NIH (ACTIV-4d and Host Tissue-Nectar Trial). M. N. G. reports a grant from the National Heart, Lung, and Blood Institute (NHLBI); consulting fees for scientific advisory from Endpoint; support for attending an ATS Board of Executives Meeting; and participation in a Regeneron Data Safety and Monitoring Board (DSMB) for a monoclonal antibody trial. M. C. E. reports grants from NIH, Regeneron Pharmaceuticals, and payment from Abbott Labs for attending/lecture at the ASPEN Annual Meeting and on an Abbott webinar on nutrition in patients with COVID019. A. A. G. reports grants from NIH, Department of Defense, AbbVie, and Faron Pharmaceuticals. N. M. M. reports grants from the US CDC. E. T. M. reports grants from NIH and Merck and payment for lectures from the Michigan Infectious Diseases Society. K. W. G. reports grants from the Department of Defense and NIH support for ACTIV-4HT and Department of Defence support for Military Health System Research Symposium 2022 travel. J. H. K. is supported by grant 1K23AI137321-01A1 from the National Institute of Allergy and Infectious Diseases. N. H. reports grants from Sanofi and Quidel. A. S. L. reports grants from the US CDC, National Institute of Allergy and Infectious Diseases, and Burroughs Wellcome Fund; consulting fees from Sanofi and Roche; and membership on the American Society of Virology governing council (unpaid). C. J. L. reports grants from NIH, Department of Defense, CDC, bioMerieux, Entegrion Inc, Endpoint Health, Astra Zeneca, and AbbVie; patents for risk stratification in sepsis and septic shock issued to the Cincinnati Children's Hospital Medical Center; participation on DSMBs for clinical trials for Study Principal Investigators unrelated to the current work; and stock options in Bioscape Digital unrelated to the current work. C. G. G. reports grants from NIH, CDC, the Food and Drug Administration, the Agency for Healthcare Research and Quality, Sanofi, and Syneos Health and consulting fees from Pfizer, Merck, and Sanofi. 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., (Published by Oxford University Press on behalf of Infectious Diseases Society of America 2022.)

Background: Coronavirus disease 2019 (COVID-19) messenger RNA (mRNA) vaccines were authorized in the United States in December 2020. Although vaccine effectiveness (VE) against mild infection declines markedly after several months, limited understanding exists on the long-term durability of protection against COVID-19-associated hospitalization., Methods: Case-control analysis of adults (≥18 years) hospitalized at 21 hospitals in 18 states 11 March-15 December 2021, including COVID-19 case patients and reverse transcriptase-polymerase chain reaction-negative controls. We included adults who were unvaccinated or vaccinated with 2 doses of a mRNA vaccine before the date of illness onset. VE over time was assessed using logistic regression comparing odds of vaccination in cases versus controls, adjusting for confounders. Models included dichotomous time (<180 vs ≥180 days since dose 2) and continuous time modeled using restricted cubic splines., Results: A total of 10 078 patients were included, 4906 cases (23% vaccinated) and 5172 controls (62% vaccinated). Median age was 60 years (interquartile range, 46-70), 56% were non-Hispanic White, and 81% had ≥1 medical condition. Among immunocompetent adults, VE <180 days was 90% (95% confidence interval [CI], 88-91) versus 82% (95% CI, 79-85) at ≥180 days (P < .001). VE declined for Pfizer-BioNTech (88% to 79%, P < .001) and Moderna (93% to 87%, P < .001) products, for younger adults (18-64 years) (91% to 87%, P = .005), and for adults ≥65 years of age (87% to 78%, P < .001). In models using restricted cubic splines, similar changes were observed., Conclusions: In a period largely predating Omicron variant circulation, effectiveness of 2 mRNA doses against COVID-19-associated hospitalization was largely sustained through 9 months., Competing Interests: Potential conflicts of interest. All authors have completed and submitted the International Committee of Medical Journal Editors form for disclosure of potential conflicts of interest. W. H. S. reports grant funding from the Centers for Disease Control and Prevention (CDC) for this work, grants and consultant fees from Merck (for research on the surveillance of pneumococcal infections) and Gilead Sciences (for research on the surveillance of hepatitis C virus infections) outside this work. M. G. reports grant support from CDC (Ambulatory US Flu/COVID VE Network and Adult Inpatient Flu/COVID VE Network, HAIVEN), CDC-Abt Associates (Flu Vax Immunogenitiy RCT and RECVOERPROTECT COVID/Flu VE studies), CDC-Westat (VISION COVID Study), and Janssen (Johnson & Johnson) (RSV Severity App Birth Cohort Study). A. A. G. reports grant support from CDC, National Institute of Health (NIH), Department of Defense (DoD), AbbVie, and Faron Pharmaceuticals. J. D. C. reports grants from the CDC, NIH (K23HL153584), and Department of Defense. N. M. reports grants from the CDC (funded two other multicenter COVID-related projects separate from this work through payments to my institution). T. M. reports a grant from CDC and fees from the Society of Hospital Medicine for a talk about managing patients with congestive heart failure. K. G. reports grants from the CDC and the received grant funding for participation in executive committee of COVID-19 therapeutics from the NIH (ACTIV-4HT NECTAR Trial). D. C. F. reports grant support from CDC, consultant fees from Cytovale, and membership on a Medpace Data Safety Monitoring Board (DSMB). D. N. H. reports contracts from CDC, National Heart, Lung, and Blood Institute (NHLBI; funding for participation in the ACTIV4d - Host Tissue Trial), and Incyte Corporation (funding to enroll in RUCOVID-DEVENT) and membership on the SAFE EVICT Trial of VIT C in COVID-19 as DSMB chair. M. C. E. reports talks on nutrition in COVID pneumonia at the American Society of Parenteral and Enteral Nutrition (ASPEN) conference sponsored by Abbott Labs. M. N. G. reports grant support from CDC, NHLBI, NIH, and Agency for Healthcare Research and Quality (AHRQ), travel support for American Thoracic Society board meeting, and membership on the Regeneron DSMB for monoclonal antibodies in COVID-19. N. J. reports grants from CDC, NIH/NHLBI/NINDS, and University of Washington Royalty Research Fund, and payment for expert testimony from the Washington Department of Health. I. D. P. reports grants from CDC, NIH, Intermountain Research & Medical Foundation, and Janssen Pharmaceuticals, and institutional fees from Asahi Kasei Pharma and from Regeneron Pharmaceuticals. S. M. B. reports grants from CDC, NIH (for trials and other research activities related to COVID), and DoD (to study COVID); fees from Hamilton ventilators for chairing a DSMB; and personal fees from New York University for service on a DSMB. E. T. M. reports a grant from Merck outside the submitted work. A. M. reports grant support from CDC, NIH, NIAID, and membership on a DSMB for the Food and Drug Administration (FDA). A. K. reports grants from CDC, Gilead Sciences, Ely Lily, United Therapeutics, BOA-Medical, and 4D Medical and membership on the Guidelines Committee for Chest. C. L. H. reports grants from CDC, NIH, and the American Lung Association. A. D. reports a grant from the CDC and consulting fees from ALung Technologies (Steering Committee). J. W. reports grants from the CDC and NIH (ARREST Pneumonia Trial UH3HL141722, ACTIV3a and 3b trials, and ACTIV4a trial), and membership on the American Board of Internal Medicine Critical Care Medicine exam committee. S. Y. C. reports grants from CDC and Regeneron (for 6R88-COV-2040 trial) and consulting fees from PureTech Health (for COVID study) and Kiniska (for possible ARDS study). J. H. K. reports grant support from CDC and NIH (1K23 AI137321-01A1). A. S. L. reports grants from the CDC, NIH, and Burroughs Wellcome Fund, consultant fees for antiviral drugs from Sanofi and fees from Roche for membership on a baloxavir trial steering committee. N. H. reports grants from CDC, NIH, Sanofi, and Quidel and honoraria for speaking at a continuing medical education event at American Academy of Pediatrics. C. G. G. reports consultant fees from Pfizer, Merck, and Sanofi and grants from Syneos Health, CDC, NIH, FDA, AHRQ, and Sanofi. T. R. reports grants from CDC and Abbvie Inc, consultant fees from Cytovale, Inc. and Cumberland Pharmaceuticals Inc., membership on a Sanofi, Inc. DSMB, a voluntary role as the Immediate Past President of ASPEN and stock in Cumberland Pharmaceuticals, Inc. I. J. reports grants/contracts from the CDC, NIH, Quidel, and Sanofi. C. J. L. reports grants/contracts from CDC, NIH, DoD, bioMerieux, Endpoint Health, Entegrion, Inc., and AbbVie; a patent issued to Cincinnati Children’s Hospital Medical Center for risk stratification in sepsis and septic shock, membership on a Study Principal Investigators DSMB for clinical trials unrelated to the current work, Executive Committee; Immediate Past President, Member, Board of Directors, Association for Clinical and Translational Science, and stock options in Bioscape Digita unrelated to the current work. W. B. S. reports a grant from the CDC and NIH (5K12HL133117-05). 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., (Published by Oxford University Press on behalf of the Infectious Diseases Society of America 2022.)

Background: Coronavirus disease 2019 (COVID-19) vaccine effectiveness (VE) studies are increasingly reporting relative VE (rVE) comparing a primary series plus booster doses with a primary series only. Interpretation of rVE differs from traditional studies measuring absolute VE (aVE) of a vaccine regimen against an unvaccinated referent group. We estimated aVE and rVE against COVID-19 hospitalization in primary-series plus first-booster recipients of COVID-19 vaccines., Methods: Booster-eligible immunocompetent adults hospitalized at 21 medical centers in the United States during December 25, 2021-April 4, 2022 were included. In a test-negative design, logistic regression with case status as the outcome and completion of primary vaccine series or primary series plus 1 booster dose as the predictors, adjusted for potential confounders, were used to estimate aVE and rVE., Results: A total of 2060 patients were analyzed, including 1104 COVID-19 cases and 956 controls. Relative VE against COVID-19 hospitalization in boosted mRNA vaccine recipients versus primary series only was 66% (95% confidence interval [CI], 55%-74%); aVE was 81% (95% CI, 75%-86%) for boosted versus 46% (95% CI, 30%-58%) for primary. For boosted Janssen vaccine recipients versus primary series, rVE was 49% (95% CI, -9% to 76%); aVE was 62% (95% CI, 33%-79%) for boosted versus 36% (95% CI, -4% to 60%) for primary., Conclusions: Vaccine booster doses increased protection against COVID-19 hospitalization compared with a primary series. Comparing rVE measures across studies can lead to flawed interpretations of the added value of a new vaccination regimen, whereas difference in aVE, when available, may be a more useful metric., (© The Author(s) 2022. Published by Oxford University Press on behalf of Infectious Diseases Society of America.)