tetano
Editor, Senior Moderator
J Infect Dis
. 2026 Oct 31:jiag538.
doi: 10.1093/infdis/jiag538. Online ahead of print.
Jessica R Meeker 1 , Ashley M Price 1 , Emily Martin 2 , Ivana Vaughn 3 , Karen J Wernli 4 , C Hallie Phillips 4 , Manjusha J Gaglani 5 6 , Chandni Raiyani 5 6 , Huong Q Nguyen 7 , Jennifer P King 7 , Stacey House 8 , Jamie Mills 8 , Vel Murugan 9 , Lora Nordstrom 10 , Elie Saade 11 , Kiran Faryar 11 , Richard K Zimmerman 12 , Krissy Moehling Geffel 12 , Emmanuel B Walter 13 , Natalie A B Bontrager 13 , Jessie R Chung 1 , Brendan Flannery 1 , Sascha Ellington 1 ; US Flu VE Network Investigators
Collaborators, Affiliations Expand
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.
Keywords: B/Victoria; B/Yamagata; antigenic drift; influenza; influenza B; influenza vaccine; test-negative design; vaccine effectiveness.
. 2026 Oct 31:jiag538.
doi: 10.1093/infdis/jiag538. Online ahead of print.
Influenza B Circulation and Vaccine Effectiveness Against Medically Attended Outpatient Influenza B Illness, United States, 2016-17 Through 2024-25
Jessica R Meeker 1 , Ashley M Price 1 , Emily Martin 2 , Ivana Vaughn 3 , Karen J Wernli 4 , C Hallie Phillips 4 , Manjusha J Gaglani 5 6 , Chandni Raiyani 5 6 , Huong Q Nguyen 7 , Jennifer P King 7 , Stacey House 8 , Jamie Mills 8 , Vel Murugan 9 , Lora Nordstrom 10 , Elie Saade 11 , Kiran Faryar 11 , Richard K Zimmerman 12 , Krissy Moehling Geffel 12 , Emmanuel B Walter 13 , Natalie A B Bontrager 13 , Jessie R Chung 1 , Brendan Flannery 1 , Sascha Ellington 1 ; US Flu VE Network Investigators
Collaborators, Affiliations Expand
- PMID: 42965317
- DOI: 10.1093/infdis/jiag538
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.
Keywords: B/Victoria; B/Yamagata; antigenic drift; influenza; influenza B; influenza vaccine; test-negative design; vaccine effectiveness.