Influenza vaccine effectiveness against hospitalizations and emergency department or urgent care encounters for children, adolescents, and adults during the 2023-2024 season, United States

Published in the Clinical infectious diseases : an official publication of the Infectious Diseases Society of America. Here is a link to the article.

Regenstrief Institute authors: Shaun Grannis, M.D., MS, Brian E. Dixon, PhD, MPA, Colin Rogerson, M.D., MPH

Abstract

Background: The 2023-2024 influenza season had predominant influenza A(H1N1)pdm09 virus activity, but A(H3N2) and B viruses co-circulated. Seasonal influenza vaccine strains were well-matched to these viruses.

Methods: Using health care encounters data from health systems in 8 states, we evaluated influenza vaccine effectiveness (VE) against influenza-associated medical encounters from October 2023-April 2024. Using a test-negative design, we compared the odds of vaccination between patients with an acute respiratory illness (ARI) who tested positive (cases) versus negative (controls) for influenza by molecular assay, adjusting for confounders. VE was stratified by age group, influenza type (overall, influenza A, influenza B), and care setting (hospitalization, emergency department or urgent care [ED/UC] encounter).

Results: Overall, 74,000 encounters in children and adolescents aged 6 months – 17 years (3,479 hospitalizations, 70,521 ED/UC encounters) and 267,606 in adults aged ≥18 years (66,828 hospitalizations, 200,778 ED/UC encounters) were included. Across care settings, among children and adolescents 15% (2,758/17,833) of cases versus 32% (18,240/56,167) of controls had received vaccination. Among adults, 25% (11,632/46,614) of cases versus 44% (97,811/220,992) of controls across care settings had received vaccination. VE was 58% (95% confidence interval [95% CI]: 44-69%) against hospitalization and 58% (95% CI: 56-60%) against ED/UC encounters for children and adolescents, and 39% (95% CI: 35-43) against hospitalization and 47% (95% CI: 46-49%) against ED/UC encounters for adults. Across age groups, VE was higher against influenza B than influenza A.

Conclusions: Influenza vaccines provided protection against influenza-associated illness across health care settings and age groups during the 2023-2024 influenza season.

Authors: 

Mark W Tenforde ¹, Emily L Reeves ¹, Zachary A Weber ², Sara Y Tartof ³, Nicola P Klein ⁴, Kristin Dascomb ⁵, Malini B DeSilva ⁶, Duck-Hye Yang ², Shaun J Grannis ^7 8, Stephanie A Irving ⁹, Toan C Ong ¹⁰, Ruth Link-Gelles ^1 11, S Bianca Salas ³, Lina S Sy ³, Bruno Lewin ³, Richard Contreras ³, Ousseny Zerbo ⁴, Bruce Fireman ⁴, John Hansen ⁴, Julius Timbol ⁴, Tamara Sheffield ⁵, Daniel Bride ⁵, Julie Arndorfer ⁵, Josh VanOtterloo ⁵, Charlene E McEvoy ⁶, Omobosola O Akinsete ⁶, Inih J Essien ⁶, Brian E Dixon ^7 12, Colin Rogerson ^7 8, William F Fadel ^7 12, Thomas Duszynski ¹², Allison L Naleway ⁹, Michelle A Barron ¹³, Suchitra Rao ¹⁴, David Mayer ¹⁰, Catia Chavez ¹⁰, Sarah W Ball ², Amanda B Payne ¹, Caitlin Ray ¹, Monica Dickerson ¹, Varsha Neelam ¹, Katherine Adams ¹, Brendan Flannery ¹, Jennifer DeCuir ^1 11, Shikha Garg ^1 11

Affiliations: 

1National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia, United States.
2Westat, Rockville, Maryland, United States.
3Department of Research & Evaluation, Kaiser Permanente Southern California, Pasadena, California, United States.
4Kaiser Permanente Vaccine Study Center, Kaiser Permanente Northern California Division of Research, Oakland, California, United States.
5Division of Infectious Diseases and Clinical Epidemiology, Intermountain Health, Salt Lake City, Utah, United States.
6HealthPartners Institute, Minneapolis, Minnesota, United States.
7Center for Biomedical Informatics, Regenstrief Institute, Indianapolis, Indiana, United States.
8School of Medicine, Indiana University, Indianapolis, Indiana, United States.
9Kaiser Permanente Center for Health Research, Portland, Oregon, United States.
10Department of Biomedical Informatics, University of Colorado Anschutz Medical Campus, Aurora, Colorado, United States.
11United States Public Health Service Commissioned Corps, Rockville, Maryland, United States.
12Fairbanks School of Public Health, Indiana University, Indianapolis, Indiana, United States.
13Department of Medicine, University of Colorado Anschutz Medical Campus, Aurora, Colorado, United States.
14Department of Pediatrics, University of Colorado Anschutz Medical Campus, Aurora, Colorado, United States.