Effect of vaccination on the prevention of influenza-related severe illness in adults attended in a third level hospital during the 2017-2018 epidemic season

Objectives: The objective of this research was to evaluate the effect of influenza vaccination on the prevention of influenza-related severe cases in adults treated in a third-level hospital during the 2017-2018 epidemic season. Methodology: A descriptive analysis was performed on the entire population of subjects with a laboratory-confirmed influenza test during the 2017-2018 season. A severe case was defined as a patient treated in one of the Intensive Care Units (ICUs) and/or death. The effect of the vaccine on the adult population was determined by multivariate logistic regression analysis. Results: Between epidemiological weeks 44/2017 and 19/2018, the hospital's laboratory detected 706 positive samples for influenza virus. Of the 551 confirmed patients aged 18 years or older, forty-three were admitted to one of the ICUs, and 26 died during admission. The explanatory multivariate model has shown that flu vaccination prior to or during the epidemic season was a protective factor for the development of severity [OR:0.27 (0.11-0.65, p = 0.004)], adjusted by age [OR: 1.03 (1.01-1.06), p=.04], sex, type of virus (H1N1-pdm09, H3N2 or B virus), Chronic Complex Patient index or Advanced Chronic Disease index. Conclussions: Influenza vaccination is a protective factor against the development of severity associated with influenza infection in a season when vaccination did not contain the virus with higher epidemic circulation among the population. Flu vaccination should be recommended annually following the guidelines established by the health authorities. (C) 2020 Elsevier Espana, S.L.U. All rights reserved.