COVID-19 Evidence Alerts
from McMaster PLUSTM

Current best evidence for clinical care (more info)

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Etiology Del Riccio M, Lorini C, Bonaccorsi G, et al. The Association between Influenza Vaccination and the Risk of SARS-CoV-2 Infection, Severe Illness, and Death: A Systematic Review of the Literature. Int J Environ Res Public Health. 2020 Oct 27;17(21). pii: ijerph17217870. doi: 10.3390/ijerph17217870.

We reviewed the association between seasonal influenza vaccination and the risk of SARS-CoV-2 infection or complicated illness or poor outcome (e.g., severe disease, need for hospitalization or ventilatory support, or death) among COVID-19 patients. None of the studies that were reviewed (n = 12) found a significant increase in the risk of infection or in the illness severity or lethality, and some reported significantly inverse associations. Our findings support measures aimed at raising influenza vaccination coverage in the coming months.

Discipline / Specialty Area Score
Hospital Doctor/Hospitalists
Internal Medicine
Family Medicine (FM)/General Practice (GP)
General Internal Medicine-Primary Care(US)
Infectious Disease
Public Health
Comments from MORE raters

Family Medicine (FM)/General Practice (GP) rater

As the authors state themselves, "it must be acknowledged that all reviewed studies are retrospective and observational in nature, and thus likely to be subject to bias, and that not all studies reported measures of association adjusted by the relevant confounders". So a cause-effect relation between influenza vaccination and (less) risk of COVID19 infections has not definitely been established.