[Association between influenza vaccination and mortality due to COVID-19].

Background: It has recently been suggested that influenza vaccination may be a factor associated with decreased COVID-19 mortality.

Methods: An age-matched case-control study based on hospital cases. We included subjects aged 18 years and older with a diagnosis of moderate to severe COVID-19. Infection was corroborated by RT-PCR test for SARS-COV-2. Deceased subjects were considered cases, controls were patients discharged due to improvement of acute symptoms. We used bivariate analysis to determine factors associated with death from COVID-19, and calculated odds ratios and 95% confidence intervals.

Results: A total of 560 patients were included in the study, 214 (38.2%) were considered cases and 346 (61.7%) controls. A significant difference was observed with the presence of type 2 diabetes mellitus [54% vs. 39.3% between cases and controls, respectively (p=.04)] and having received influenza vaccination (p= .02). Type 2 diabetes mellitus was associated with higher COVID-19 mortality [OR 1.8 (95% CI 1.2-2.5) p=.01], whereas having been immunised against influenza in 2019 was associated with lower mortality in this group of patients [OR .6 (95% CI .4-.9) p=.02].

Conclusions: Influenza vaccination in the previous year appears to be associated with lower mortality from COVID-19; whereas type 2 diabetes mellitus is confirmed as a condition associated with higher mortality.