Flu vaccine may lessen ventilation risk in COVID-19

Patients immunized with the influenza vaccine see significant protection against mechanical ventilation in COVID-19, a recent study has found.

Drawing from the online databases of PubMed, Embase, Web of Science, Scopus, OVID, and the Cochrane Central database, researchers conducted quantitative synthesis of 16 observational studies totaling 191,496 COVID-19 patients.

Pooled analysis of four studies (n=1,716) showed that COVID-19 patients who had had the flu vaccine were nearly 30 percent less likely to need mechanical ventilation than comparators who were unvaccinated (risk ratio [RR], 0.72, 95 percent confidence interval [CI], 0.54–0.96; p=0.03). Findings did not show significant heterogeneity.

Influenza immunization showed no significant impact on other COVID-19 outcomes, however. Mortality, for instance, was not significantly affected by the flu vaccine (RR, 1.20, 95 percent CI, 0.71–2.04; p=0.5), as were hospital admission (RR, 1.04, 95 percent CI, 0.84–1.29; p=0.75) and intensive care admission (RR, 0.84, 95 percent CI, 0.44–1.62; p=0.60).

Similarly, flu vaccination did not significantly reduce duration of either hospitalization (mean difference [MD], –0.16 days, 95 percent CI, –2.76 to 2.45; p=0.91) or intensive care admission (MD, 0.99 days, 95 percent CI, –2.15 to 4.13; p=0.54).

Vaccinated and unvaccinated groups also showed similar rates of symptomatic and asymptomatic disease.

“Future research of high-quality randomized controlled trials is recommended to further assess the efficacy of the influenza vaccine in COVID-19 patients,” the researchers said. “The regular updating of the influenza vaccine should also be put into consideration. Other possible important confounding factors should also be taken into consideration, such as patient’s health literacy, and socioeconomic status.”