In a new study, researchers found that people who received a flu shot last flu season were much less likely to test positive for a COVID-19 infection when the pandemic hit.
And those who did test positive for COVID-19 had fewer complications if they received their flu shot.
The research was conducted by a team at Michigan Medicine.
In the study, the team reviewed medical charts for more than 27,000 patients who were tested for a COVID-19 infection between March and mid-July of 2020.
Of the nearly 13,000 who got a flu shot in the previous year, 4% tested positive for COVID-19. Of the 14,000 who hadn’t gotten a flu shot, nearly 5% tested positive for COVID-19.
The association remained strong after controlling for other variables including ethnicity, race, gender, age, BMI, smoking status and many comorbid health conditions.
People who received their flu shot were also much less likely to require hospitalization, although the researchers didn’t find a big difference in mortality between the two groups.
No one in the study tested positive for both infections at the same time.
The team says instead of a concerning connection between COVID-19 and the flu shot, their findings provide more confidence that getting your flu shot is linked to staying out of the hospital for COVID-19.
The underlying mechanism behind the association isn’t yet clear.
It is possible that patients who receive their flu vaccine are also people who are practicing more social distancing and following CDC guidelines.
However, it is also plausible that there could be a direct biological effect of the flu vaccine on the immune system relevant for the fight against the SARS-CoV-2 virus.
One author of the study is Marion Hofmann Bowman, M.D.
The study is published in the American Journal of Infection Control.
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