Association between influenza vaccination and mortality due to COVID-19

Abstract

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 = 0.04)] and having received influenza vaccination (P = 0.02). Type 2 diabetes mellitus was associated with higher COVID-19 mortality [OR 1.8 (95% CI 1.2–2.5) P = 0.01], whereas having been immunised against influenza in 2019 was associated with lower mortality in this group of patients [OR 0.6 (95% CI 0.4–0.9) P = 0.02].

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.

Resumen

Antecedentes

Recientemente se ha sugerido que la vacunación contra la influenza puede ser un factor asociado con la disminución de la mortalidad por la Coronavirus Disease 2019 (COVID-19).

Métodos

Mediante un estudio de casos y controles pareado por edad, basado en casos hospitalarios incluimos sujetos de 18 años en adelante con diagnóstico de COVID-19 moderado a grave. La infección se corroboró por RT-PCR para SARS-CoV-2. Los sujetos fallecidos fueron considerados casos, los controles fueron los pacientes que egresaron por mejoría del cuadro agudo. Se utilizó análisis bivariado, para determinar los factores asociados con la muerte por COVID-19, con cálculo de razón de momios e intervalos de confianza del 95%.

Resultados

Un total de 560 pacientes fueron incluidos en el estudio, 214 (38,2%) fueron considerados casos y 346 (61,7%) controles. Se observó diferencia significativa con la presencia de diabetes mellitus tipo 2 [54% vs. 39,3% entre casos y controles, respectivamente (p = 0,04)] y haber recibido la vacuna contra la influenza (p = 0,02). La diabetes mellitus tipo 2 se asoció con mayor mortalidad por COVID-19 [OR 1,8 (IC 95% 1,2-2,5) p = 0,01], mientras que el haberse inmunizado contra influenza en 2019 se asoció con menor mortalidad en este grupo de pacientes [OR 0,6 (IC 95% 0,4-0,9) p = 0,02].

Conclusiones

La vacunación contra influenza en el año previo parece asociarse con una menor mortalidad por COVID-19, mientras que se confirma a la diabetes mellitus tipo 2 como una condición asociada con mayor mortalidad.