Abstract
Following an extremely low incidence of influenza during the first waves of the ongoing COVID-19 pandemic, the 2021/22 Northern Hemisphere winter season saw a resurgence of influenza virus circulation. The aim of this study was to describe epidemiology of severe acute respiratory infections (SARIs) among Italian adults and estimate the 2021/22 season influenza vaccine effectiveness. For this purpose, a test-negative case-control study was conducted in a geographically representative sample of Italian hospitals. Of 753 SARI patients analyzed, 2.5% (N = 19) tested positive for influenza, most of which belonged to the A(H3N2) subtype. Phylogenetic analysis showed that these belonged to the subclade 3C.2a1b.2a.2, which was antigenically different from the 2021/22 A(H3N2) vaccine component. Most (89.5%) cases were registered among non-vaccinated individuals, suggesting a protective effect of influenza vaccination. Due to a limited number of cases, vaccine effectiveness estimated through the Firth’s penalized logistic regression was highly imprecise, being 83.4% (95% CI: 25.8–97.4%) and 83.1% (95% CI: 22.2–97.3%) against any influenza type A and A(H3N2), respectively. Exclusion of SARS-CoV-2-positive controls from the model did not significantly change the base-case estimates. Within the study limitations, influenza vaccination appeared to be effective against laboratory-confirmed SARI.
Funder
Innovative Medicines Initiative 2 Joint Undertaking
Subject
Pharmacology (medical),Infectious Diseases,Drug Discovery,Pharmacology,Immunology
Reference38 articles.
1. Progress and remaining gaps in estimating the global disease burden of influenza;Bresee;Emerg. Infect. Dis.,2018
2. Centers for Disease Control and Prevention (CDC) (2022, August 06). Past Seasons Vaccine Effectiveness Estimates, Available online: https://www.cdc.gov/flu/vaccines-work/past-seasons-estimates.html.
3. World Health Organization (WHO) (2012). Vaccines against influenza WHO position paper–November 2012. Wkly. Epidemiol. Rec., 87, 461–476.
4. Very little influenza in the WHO European Region during the 2020/21 season, weeks 40 2020 to 8 2021;Adlhoch;Euro Surveill.,2021
5. Influenza returns with a season dominated by clade 3C.2a1b.2a.2 A(H3N2) viruses, WHO European Region, 2021/22;Melidou;Euro Surveill.,2022
Cited by
3 articles.
订阅此论文施引文献
订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献