Effectiveness of mRNA COVID-19 vaccines and hybrid immunity in preventing SARS-CoV-2 infection and symptomatic COVID-19 among adults in the United States.

Background: Understanding protection against SARS-CoV-2 infection by vaccine and hybrid immunity is important for informing public health strategies as new variants emerge.

Methods: We analyzed data from three cohort studies spanning September 1, 2022-July 31, 2023, to estimate COVID-19 vaccine effectiveness (VE) against SARS-CoV-2 infection and symptomatic COVID-19 among adults with and without prior infection in the United States. Participants collected weekly nasal swabs, irrespective of symptoms, annual blood draws, and completed periodic surveys, which included vaccination status and prior infection history.

Outbreak of Rotavirus Diarrheal Infection among Adults in King County, Washington, January-June 2023.

Rotavirus is a leading cause of diarrhea among children but less known as a cause among adults. We describe clinical, epidemiologic, and genotype characteristics of a rotavirus outbreak among adults in King County, Washington occurring January-June 2023. Adult rotavirus incidence in 2023 was ten times higher than the same period in 2022 (5% versus 0.

Maternal-Infant Respiratory Syncytial Virus and Influenza A Virus Antibody Transfer in Preterm and Full-term Infants.

Background: Immunization against influenza and respiratory syncytial virus (RSV) protects pregnant individuals and their infants against infection via transplacental transport of immunoglobulin G (IgG). We sought to evaluate the quantity and efficiency of maternal influenza- and RSV-specific IgG transfer in pregnancies with preterm and full-term deliveries.

Methods: Delivery samples from 115 maternal-infant pairs (2018-2021) were analyzed for RSV prefusion F and IAV-H3 and IAV-H1 antibodies using electrochemiluminescence assays.

Estimated Vaccine Effectiveness for Pediatric Patients With Severe Influenza, 2015-2020.

Importance: Increasing the understanding of vaccine effectiveness (VE) against levels of severe influenza in children could help increase uptake of influenza vaccination and strengthen vaccine policies globally.

Objective: To investigate VE in children by severity of influenza illness.

Design, Setting, And Participants: This case-control study with a test-negative design used data from 8 participating medical centers located in geographically different US states in the New Vaccine Surveillance Network from November 6, 2015, through April 8, 2020.

Antiviral Use Among Children Hospitalized With Laboratory-Confirmed Influenza Illness: A Prospective, Multicenter Surveillance Study.

Background: Guidelines state that all hospitalized children with suspected or confirmed influenza receive prompt treatment with influenza-specific antivirals. We sought to determine the frequency of, and factors associated with, antiviral receipt among hospitalized children.

Methods: We conducted active surveillance of children presenting with fever or respiratory symptoms from 1 December 2016 to 31 March 2020 at 7 pediatric medical centers in the New Vaccine Surveillance Network.

Respiratory Syncytial Virus Disease Burden and Nirsevimab Effectiveness in Young Children From 2023-2024.

Importance: During the 2023-2024 respiratory syncytial virus (RSV) season in the United States, 2 new RSV prevention products were recommended to protect infants in their first RSV season: nirsevimab and Pfizer's maternal RSV vaccine. Postlicensure studies are needed to assess prevention product impact and effectiveness.

Objective: To compare the epidemiology and disease burden of medically attended RSV-associated acute respiratory illness (ARI) among children younger than 5 years during the 2023-2024 RSV season with 3 prepandemic RSV seasons (2017-2020), estimate nirsevimab effectiveness against medically attended RSV-associated ARI, and compare nirsevimab binding site mutations among circulating RSV in infants with and without nirsevimab receipt.

Underutilization of Influenza Antiviral Treatment Among Children and Adolescents at Higher Risk for Influenza-Associated Complications - United States, 2023-2024.

Annually, tens of thousands of U.S. children and adolescents are hospitalized with seasonal influenza virus infection.

On-time childhood vaccination before and during the COVID-19 pandemic in seven communities: Findings from the New Vaccine Surveillance Network.

Background: The COVID-19 pandemic raised unprecedented challenges to vaccinating children. This multi-center study aimed to compare on-time vaccination of children before and during the COVID-19 pandemic and identify key factors associated with on-time vaccination.

Methods: This study was conducted among children aged 0-6 years enrolled in the New Vaccine Surveillance Network at seven geographically diverse U.

Clinical and Genomic Epidemiology of Coxsackievirus A21 and Enterovirus D68 in Homeless Shelters, King County, Washington, USA, 2019-2021.

Congregate homeless shelters are disproportionately affected by infectious disease outbreaks. We describe enterovirus epidemiology across 23 adult and family shelters in King County, Washington, USA, during October 2019-May 2021, by using repeated cross-sectional respiratory illness and environmental surveillance and viral genome sequencing. Among 3,281 participants >3 months of age, we identified coxsackievirus A21 (CVA21) in 39 adult residents (3.

Pediatric Clinical Influenza Disease by Type and Subtype 2015-2020: A Multicenter, Prospective Study.

Background: Previous investigations into clinical signs and symptoms associated with influenza types and subtypes have not definitively established differences in the clinical presentation or severity of influenza disease.

Methods: The study population included children 0 through 17 years old enrolled at 8 New Vaccine Surveillance Network sites between 2015 and 2020 who tested positive for influenza virus by molecular testing. Demographic and clinical data were collected for study participants via parent/guardian interview and medical chart review.

Prevalence of SARS-CoV-2 in Children Identified by Preprocedural Testing at 5 US Children's Hospital Systems.

Background: The burden of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in asymptomatic children was initially presumed to be high, which influenced hospital, school and childcare policies. Before vaccines were widely available, some hospitals implemented universal preprocedural SARS-CoV-2 polymerase chain reaction testing on asymptomatic patients. Understanding SARS-CoV-2 prevalence in asymptomatic children is needed to illuminate the diversity of viral characteristics and inform policies implemented during future pandemics.

Immunogenicity and Reactogenicity of High-dose or Standard-dose Influenza Vaccine in a Second Consecutive Influenza Season.

Background: Pediatric hematopoietic cell transplant (HCT) recipients are at high-risk for morbidity from influenza virus infection. We demonstrated in a primary phase II randomized controlled trial that two post-HCT doses of high-dose trivalent influenza vaccine (HD-TIV) given four weeks apart were more immunogenic than two doses of standard-dose quadrivalent influenza vaccine (SD-QIV). Herein, we present immunogenicity and safety of influenza vaccination in a consecutive season post-HCT using the same dosing regimen.

Evaluation of a Modified Vesikari Severity Score as a Research Tool for Assessing Pediatric Acute Gastroenteritis.

A modified Vesikari severity score (MVSS) is a useful research tool for assessing severity of acute gastroenteritis. We present a MVSS for studies in which a follow-up assessment of symptoms cannot be obtained. The MVSS significantly correlated with other markers of severity, including illness duration and work and school absenteeism.

Evaluation of Transplacental Maternal SARS-CoV-2 Antibody Transfer in Small for Gestational Age Infants.

Little is known about the potential benefits of maternal immunization in the setting of high-risk pregnancies resulting in small-for-gestational-age (SGA) infants. This study compares transplacental transfer of maternal SARS-CoV-2 anti-Spike antibody in pregnancies with SGA compared to appropriate-for-gestational-age infants.

The Potential Benefits of Delaying Seasonal Influenza Vaccine Selections for the Northern Hemisphere: A Retrospective Modeling Study in the United States.

Background: Antigenic similarity between vaccine viruses and circulating viruses is crucial for achieving high vaccine effectiveness against seasonal influenza. New non-egg-based vaccine production technologies could revise current vaccine formulation schedules. We aim to assess the potential benefit of delaying seasonal influenza vaccine virus selection decisions.

Transfer of Respiratory Syncytial Virus Prefusion F Protein Antibody in Low Birthweight Infants.

Background: Respiratory syncytial virus (RSV)-associated lower respiratory tract infection contributes significantly to morbidity/mortality worldwide in low birthweight (LBW) infants (<2500 g). Studies have demonstrated decreased maternal immunoglobulin G (IgG) transfer of various antibodies to LBW infants. We aimed to evaluate naturally acquired RSV anti-prefusion F protein (anti-preF) antibody transfer in pregnancies with LBW versus normal birthweight (NBW) infants.

Bivalent Omicron BA.4/BA.5 BNT162b2 Vaccine in 6-Month- to <12-Year-Olds.

Background: With the future epidemiology and evolution of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) uncertain, the use of safe and effective coronavirus disease 2019 (COVID-19) vaccines in pediatric populations remains important.

Methods: We report data from two open-label substudies of an ongoing phase 1/2/3 master study (NCT05543616) investigating the safety and immunogenicity of a variant-adapted bivalent COVID-19 vaccine encoding ancestral and Omicron BA.4/BA.