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Vaccine Effectiveness Against Influenza A(H3N2)-Associated Hospitalized Illness: United States, 2022.


ABSTRACT:

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.

SUBMITTER: Tenforde MW 

PROVIDER: S-EPMC10226741 | biostudies-literature | 2023 Mar

REPOSITORIES: biostudies-literature

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Vaccine Effectiveness Against Influenza A(H3N2)-Associated Hospitalized Illness: United States, 2022.

Tenforde Mark W MW   Patel Manish M MM   Lewis Nathaniel M NM   Adams Katherine K   Gaglani Manjusha M   Steingrub Jay S JS   Shapiro Nathan I NI   Duggal Abhijit A   Prekker Matthew E ME   Peltan Ithan D ID   Hager David N DN   Gong Michelle N MN   Exline Matthew C MC   Ginde Adit A AA   Mohr Nicholas M NM   Mallow Christopher C   Martin Emily T ET   Talbot H Keipp HK   Gibbs Kevin W KW   Kwon Jennie H JH   Chappell James D JD   Halasa Natasha N   Lauring Adam S AS   Lindsell Christopher J CJ   Swan Sydney A SA   Hart Kimberly W KW   Womack Kelsey N KN   Baughman Adrienne A   Grijalva Carlos G CG   Self Wesley H WH  

Clinical infectious diseases : an official publication of the Infectious Diseases Society of America 20230301 6


<h4>Background</h4>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.<h4>Methods</h4>To understand the effectiveness of the 2021-2022 vaccine against hospitalized influenza illness, a multistate sentinel surveillance network enro  ...[more]

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