Influenza B Circulation and Vaccine Effectiveness Against Medically Attended Outpatient Influenza B Illness, United States, 2016–17 Through 2024–25

Abstract Background Influenza B vaccine effectiveness (VE) has varied by season, lineage, antigenic drift, and vaccine composition. After B/Yamagata detection ceased globally, trivalent vaccines containing B/Victoria were reintroduced in 2024–25. We evaluated influenza B circulation and VE across eight analyzed seasons spanning this transition. Methods Ambulatory patients aged ≥6 months with acute respiratory illness were enrolled at U.S. Flu VE Network sites during eight influenza seasons from 2016–17 through 2024–25; 2020–21 was excluded because influenza circulation was negligible. Participants were tested by RT-PCR. Lineage-specific VE was estimated using a test-negative design and logistic regression adjusted for age, sex, race/ethnicity, calendar time, and study site. VE was reported for season-lineage strata with ≥50 influenza B cases. Results Among 65,773 participants, 3,629 influenza B cases were included in lineage-specific VE analyses (1,507 B/Yamagata; 2,122 B/Victoria). Six of 10 season-lineage strata met the reporting threshold. B/Victoria VE was 58% (95% CI, 28%–77%) in 2016–17, 51% (43%–57%) in 2019–20, 78% (71%–84%) in 2023–24, and 39% (14%–56%) in 2024–25. B/Yamagata VE was 55% (46%–63%) in 2016–17 and 49% (40%–56%) in 2017–18. Conclusions Influenza vaccines protected against medically attended outpatient influenza B illness, although VE varied by season. Continued VE monitoring and genetic surveillance are needed to detect emerging influenza B viruses and inform vaccine strain selection.

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Publication Details

Journal
The Journal of Infectious Diseases
Published
2026-10-30
DOI
https://doi.org/10.1093/infdis/jiag538
Primary Topic
Influenza Virus Research Studies
Type
article
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article

Influenza B Circulation and Vaccine Effectiveness Against Medically Attended Outpatient Influenza B Illness, United States, 2016–17 Through 2024–25

Elie Antoun Saade, Spencer Rose, Marcus Volz, Emmanuel B. Walter et al.
The Journal of Infectious Diseases
Influenza Virus Research Studies
article

Influenza B Circulation and Vaccine Effectiveness Against Medically Attended Outpatient Influenza B Illness, United States, 2016–17 Through 2024–25

Elie Antoun Saade, Spencer Rose, Marcus Volz, Emmanuel B. Walter, Muralidhar Jatla, Keith Stone, Emily Toth Martin, Brendan L. Flannery, Vel Murugan, Manohar B. Mutnal, C. Hallie Phillips, Richard Kent Zimmerman, Jessica Meeker, Chandni Raiyani, Stacey L. House, Kayan Dunnigan, Jason A. Ettlinger, Nicole Calhoun, Ivana A. Vaughn, Amanda McKillop, Sascha Ellington, Karen J. Wernli, Kiran A. Faryar, Lora Nordstrom, Jessie R. Chung, Leah Odame‐Bamfo, Arundhati Rao, Tresa McNeal, Huong Q. Nguyen, Eric Hoffman, Manjusha Gaglani, Jennifer P. King, Natalie A.B. Bontrager, A. Jackson, Madhava Beeram, Jason D. Ramm, Elisa Priest, US Flu VE Network Investigators, Jamie Mills, Jennifer Thomas, Javed Butler, Jesus Vallejo, Britain Fairall, Courtney Shaver, Krissy Moehling Geffel, Dedra Preece, Monica Bennett
article en

Abstract

Abstract Background Influenza B vaccine effectiveness (VE) has varied by season, lineage, antigenic drift, and vaccine composition. After B/Yamagata detection ceased globally, trivalent vaccines containing B/Victoria were reintroduced in 2024–25. We evaluated influenza B circulation and VE across eight analyzed seasons spanning this transition. Methods Ambulatory patients aged ≥6 months with acute respiratory illness were enrolled at U.S. Flu VE Network sites during eight influenza seasons from 2016–17 through 2024–25; 2020–21 was excluded because influenza circulation was negligible. Participants were tested by RT-PCR. Lineage-specific VE was estimated using a test-negative design and logistic regression adjusted for age, sex, race/ethnicity, calendar time, and study site. VE was reported for season-lineage strata with ≥50 influenza B cases. Results Among 65,773 participants, 3,629 influenza B cases were included in lineage-specific VE analyses (1,507 B/Yamagata; 2,122 B/Victoria). Six of 10 season-lineage strata met the reporting threshold. B/Victoria VE was 58% (95% CI, 28%–77%) in 2016–17, 51% (43%–57%) in 2019–20, 78% (71%–84%) in 2023–24, and 39% (14%–56%) in 2024–25. B/Yamagata VE was 55% (46%–63%) in 2016–17 and 49% (40%–56%) in 2017–18. Conclusions Influenza vaccines protected against medically attended outpatient influenza B illness, although VE varied by season. Continued VE monitoring and genetic surveillance are needed to detect emerging influenza B viruses and inform vaccine strain selection.

The Journal of Infectious Diseases
Centers for Disease Control and Prevention (US), Kaiser Permanente Washington Health Research Institute (US), Henry Ford Health System (US), University of Pittsburgh (US), Duke University (US), Baylor College of Medicine (US), Washington University in St. Louis (US), University of Michigan (US), University Hospitals of Cleveland (US), Baylor Scott & White Medical Center - Temple (US), Pittsburgh Public Schools (US), Valleywise Health (US), Baylor Scott & White Health (US), Marshfield Clinic Research Foundation (US), Marshfield Clinic Research Institute (US), Arizona State University (US)
Openalex Percentile: Top 12%
Influenza Virus Research Studies
DOISourceOpenAlex
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