End of season 2022/2023 quadrivalent influenza vaccine effectiveness in preventing influenza in primary care in Portugal

• DOI: 10.1080/21645515.2023.2263219
• Publication Date: 2023-11-15T08:04:02Z
• Authors: Irina Kislaya; Ana Rita Torres; Licínia Gomes; Aryse Melo; Ausenda Machado; Camila Henriques; Nuno Verdasca; Raquel Guiomar; Ana Paula Rodrigues; National Influenz...
• Keywords: Influenza season

Using a test-negative case–control design, we aim to estimate influenza vaccine effectiveness (VE) against medically attended laboratory-confirmed in Portugal 2022/2023 season. Between week 41/2022 and 14/2023, data on 592 patients with influenza-like illness aged 18 or more years old were collected by the national sentinel surveillance system primary care settings. Of those, 218 positive for 374 negative controls. We estimated seasonal VE as (1-odds ratio)*100% of being vaccinated cases vs. controls using logistic regression model adjusted age group, sex, presence chronic conditions, month symptoms onset. The was 59.3% (95% confidence interval (CI): 27.3 77.3) any not statistically significant 44.5% CI: −5.6 70.8) A (H3N2). In season, characterized early low activity predominant (H3N2) circulation, vaccination provided moderate protection care.