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. 2023 May;28(21):2300116.
doi: 10.2807/1560-7917.ES.2023.28.21.2300116.

Interim 2022/23 influenza vaccine effectiveness: six European studies, October 2022 to January 2023

Esther Kissling  1 , Marine Maurel  1 , Hanne-Dorthe Emborg  2 , Heather Whitaker  3 , Jim McMenamin  4 , Jennifer Howard  1 , Ramona Trebbien  5 , Conall Watson  3 , Beth Findlay  4 , Francisco Pozo  6   7 , Amanda Bolt Botnen  5 , Ciaran Harvey  4 , Angela Rose  1 ; European IVE group  8 ; Members of the European IVE group
Collaborators, Affiliations

Interim 2022/23 influenza vaccine effectiveness: six European studies, October 2022 to January 2023

Esther Kissling et al. Euro Surveill. 2023 May.

Abstract

BackgroundBetween October 2022 and January 2023, influenza A(H1N1)pdm09, A(H3N2) and B/Victoria viruses circulated in Europe with different influenza (sub)types dominating in different areas.AimTo provide interim 2022/23 influenza vaccine effectiveness (VE) estimates from six European studies, covering 16 countries in primary care, emergency care and hospital inpatient settings.MethodsAll studies used the test-negative design, but with differences in other study characteristics, such as data sources, patient selection, case definitions and included age groups. Overall and influenza (sub)type-specific VE was estimated for each study using logistic regression adjusted for potential confounders.ResultsThere were 20,477 influenza cases recruited across the six studies, of which 16,589 (81%) were influenza A. Among all ages and settings, VE against influenza A ranged from 27 to 44%. Against A(H1N1)pdm09 (all ages and settings), VE point estimates ranged from 28% to 46%, higher among children (< 18 years) at 49-77%. Against A(H3N2), overall VE ranged from 2% to 44%, also higher among children (62-70%). Against influenza B/Victoria, overall and age-specific VE were ≥ 50% (87-95% among children < 18 years).ConclusionsInterim results from six European studies during the 2022/23 influenza season indicate a ≥ 27% and ≥ 50% reduction in disease occurrence among all-age influenza vaccine recipients for influenza A and B, respectively, with higher reductions among children. Genetic virus characterisation results and end-of-season VE estimates will contribute to greater understanding of differences in influenza (sub)type-specific results across studies.

Keywords: Europe; influenza; multicentre study; test-negative design; vaccine effectiveness.

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Conflict of interest statement

Conflict of interest: None declared.

Figures

Figure 1
Figure 1
Countries providing interim influenza vaccine effectiveness results, Europe, influenza season 2022/23 (n  = 16)
Figure 2
Figure 2
Proportion of influenza virus (sub)type infections, six European studies, interim influenza season 2022/23 (n = 20,536)a
See this image and copyright information in PMC

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