Vaccines (Jul 2021)

Association of Influenza Vaccination and Prognosis in Patients Testing Positive to SARS-CoV-2 Swab Test: A Large-Scale Italian Multi-Database Cohort Study

  • Marco Massari,
  • Stefania Spila-Alegiani,
  • Massimo Fabiani,
  • Valeria Belleudi,
  • Gianluca Trifirò,
  • Ursula Kirchmayer,
  • Francesca Romana Poggi,
  • Pamela Mancuso,
  • Francesca Menniti-Ippolito,
  • Rosa Gini,
  • Claudia Bartolini,
  • Olivia Leoni,
  • Michele Ercolanoni,
  • Filippo Da-Re,
  • Stefano Guzzinati,
  • Nicoletta Luxi,
  • Flavia Riccardo,
  • Paolo Giorgi-Rossi

DOI
https://doi.org/10.3390/vaccines9070716
Journal volume & issue
Vol. 9, no. 7
p. 716

Abstract

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To investigate the association of the 2019–2020 influenza vaccine with prognosis of patients positive for SARS-CoV-2A, a large multi-database cohort study was conducted in four Italian regions (i.e., Lazio, Lombardy, Veneto, and Tuscany) and the Reggio Emilia province (Emilia-Romagna). More than 21 million adults were residing in the study area (42% of the population). We included 115,945 COVID-19 cases diagnosed during the first wave of the pandemic (February–May, 2020); 34.6% of these had been vaccinated against influenza. Three outcomes were considered: hospitalization, death, and intensive care unit (ICU) admission/death. The adjusted relative risk (RR) of being hospitalized in the vaccinated group when compared with the non-vaccinated group was 0.87 (95% CI: 0.86–0.88). This reduction in risk was not confirmed for death (RR = 1.04; 95% CI: 1.01–1.06), or for the combined outcome of ICU admission or death. In conclusion, our study, conducted on the vast majority of the population during the first wave of the pandemic in Italy, showed a 13% statistically significant reduction in the risk of hospitalization in some geographical areas and in the younger population. No impact of seasonal influenza vaccination on COVID-19 prognosis in terms of death and death or ICU admission was estimated.

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