Evidence map›Paper›PMID 42560010›Full record

ArticleInfluenza and other respiratory viruses2026

Effectiveness of Influenza Vaccines and Duration of Protection Against Hospitalisation During the 2024/25 Season in Northern Ireland, UK.

Magda Bucholc, Siobhán Murphy, Mark G O'Doherty, Suzanne Wilton, Emma Dickson, Declan T Bradley

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Article in Influenza and other respiratory viruses, 2026. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Not yet cited in PubMed.

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1 · What the graph read from it

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3 · Its place in the literature

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4 · The record

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5 · Who and what money

Authors and funding

6 authors.

Magda BucholcPublic Health Agency, Belfast, UK.ORCID https://orcid.org/0000-0002-8417-1602
Siobhán MurphyPublic Health Agency, Belfast, UK.ORCID https://orcid.org/0000-0001-9765-3873
Mark G O'DohertyPublic Health Agency, Belfast, UK.
Suzanne WiltonPublic Health Agency, Belfast, UK.
Emma DicksonPublic Health Agency, Belfast, UK.ORCID https://orcid.org/0009-0007-3178-2550
Declan T BradleyPublic Health Agency, Belfast, UK.ORCID https://orcid.org/0000-0003-1468-1823

Funding

Public Health Agency
6 · The paper itself

Abstract

backgroundSeasonal influenza causes substantial morbidity and hospitalisation each year. We estimated influenza vaccine effectiveness (VE) against laboratory-confirmed influenza-associated hospitalisation among patients in Northern Ireland (NI) during the 2024/25 influenza season.

methodsWe used a test-negative design to estimate VE against hospitalisation. Influenza-positive cases and test-negative controls were identified through the national laboratory surveillance system and linked to hospital admission and vaccination records. VE was estimated by influenza type/subtype, age group, sex, vaccine type and time since vaccination.

resultsAmong 15,133 hospitalised patients, 2024 (13.4%) tested positive for influenza. Among the 2024 patients admitted with laboratory-confirmed influenza, the vast majority tested positive for influenza A (n = 1803; 89.1%), whereas 221 cases (10.9%) were influenza B. Subtyping of influenza A identified 606 A(H1) infections and 93 A(H3) infections; the remaining 1104 influenza A samples were not subtyped. VE against laboratory-confirmed influenza infection was 46.0% (95% CI: 39.7% to 51.8%), with higher VE in children aged 2-17 years (60.8%; 95% CI: 48.3% to 70.5%) than in adults aged 18-64 years (40.5%; 95% CI: 24.9% to 53.2%) and ≥ 65 years (42.3%; 95% CI: 33.2% to 50.1%). VE against influenza A across all ages was 41.4% (95% CI: 34.2% to 47.9%). Vaccination reduced the odds of hospitalisation due to influenza A(H1) by 44.3% (95% CI: 33.2% to 53.7%) and A(H3) by 49.9% (95% CI: 20.3% to 69.3%). VE against influenza B was higher at 76.4% (95% CI: 64.9% to 84.7%). For influenza A, VE was highest 2-8 weeks after vaccination at 51.9% (95% CI: 42.1% to 60.1%) and declined with time since vaccination to 44.6% (95% CI: 35.6% to 52.5%) at 9-16 weeks and 41.4% (95% CI: 15.4% to 60.1%) at ≥ 16 weeks. VE against influenza B remained high throughout the season. No statistically significant differences in VE by vaccine type were found.

conclusionsInfluenza vaccination reduced the risk of hospitalisation with laboratory-confirmed influenza during the 2024/25 season, offering meaningful protection at individual and population levels, with the greatest benefit observed in children.

Indexed as

HospitalizationInfluenza, HumanInfluenza VaccinesVaccine EfficacyAdolescentAdultAgedAged, 80 and overChildChild, PreschoolFemaleHumansInfantInfluenza A virusInfluenza B virusMaleInfluenza Vaccineshospital admissionhospitalisationinfluenzainfluenza Ainfluenza Bvaccinevaccine effectivenessvaccine type

Identifiers

PMID42560010
PMCPMC13446018

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Read under generation 80e0d062 · epoch 390. Bibliography from PubMed, PubMed Central and OpenAlex; grants from NIH RePORTER; trial links from ClinicalTrials.gov; estimates, votes and beliefs from the OpenQuestion graph.