Flu vaccine administration in the period before SARS-CoV-2 infection and its outcomes: An umbrella review

Paolo Matteo Angeletti; Serena Marchi; Claudia Maria Trombetta; Emma Altobelli

doi:10.1016/j.pmedr.2023.102575

Flu vaccine administration in the period before SARS-CoV-2 infection and its outcomes: An umbrella review

Prev Med Rep. 2023 Dec 27:38:102575. doi: 10.1016/j.pmedr.2023.102575. eCollection 2024 Feb.

Authors

Paolo Matteo Angeletti^{1

2}, Serena Marchi³, Claudia Maria Trombetta³, Emma Altobelli¹

Affiliations

¹ Department of Life, Health and Environmental Sciences, Section of Epidemiology and Biostatistics Unit, University of L'Aquila, Piazzale Salvatore Tommasi 1, 67100 L'Aquila, Coppito (AQ), Italy.
² Cardiovascular Department, UO of Cardiac Anesthesia of the IRCCS Humanitas Research Hospital, Rozzano, Italy.
³ Department of Molecular and Developmental Medicine, University of Siena, Siena, Italy.

Abstract

Objective: The potential association between influenza vaccination and SARS-CoV-2 infection and related outcomes is still controversial. The aim of this umbrella review is to represent the impact of previous influenza vaccination and COVID-19 outcomes using evidence currently available in literature.

Methods: A literature search of MEDLINE, EMBASE, Scopus, Web of Science and Cochrane Library was conducted. The paper selection was conducted using the preferred reporting items for systematic reviews and meta-analyses (PRISMA) method by two-blinded authors. The quality of meta-analyses was assessed using the AMSTAR 2 scale (A MeaSurement Tool to Assess systematic Reviews). The outcomes investigated were SARS-CoV-2 infection after influenza vaccination, hospitalization, intensive care unit admission, mechanical ventilation and mortality.

Results: The literature research identified 7 ecological studies and 6 meta-analyses. All the ecological studies show a negative relationship between influenza vaccination and COVID-19. The meta-analyses suggest a protective action of influenza vaccination against SARS-CoV-2 infection. Regarding the outcomes evaluated, only two studies reported a statistically significant reduction of 12% and of 17% in hospitalization and intensive care unit admission, respectively. Regarding mechanical ventilation, three studies showed a risk reduction of 31%, 27% and 28%. A substantial reduction of mortality risk was also observed in one study.

Conclusions: These results suggest that influenza vaccination could be associated with reduced susceptibility to SARS-CoV-2 infection, mechanical ventilation and mortality. Our findings highlighted how the administration of flu vaccine in subjects at risk could lead to a reduction in mortality, particularly in the over 65y.

Keywords: COVID-19; Hospitalization; Influenza vaccination; Mortality; SARS-CoV-2 infection.

Publication types

Review