Photo: Stephanie King/Michigan Medicine (the academic medical center of the University of Michigan)
People who received a flu shot last flu season were significantly less likely to test positive for a COVID-19 infection when the pandemic hit, according to a new study. And those who did test positive for COVID-19 had fewer complications if they received their flu shot.
These new findings mean senior author Marion Hofmann Bowman, M.D., is continuing to recommend the flu shot to her patients even as the flu season may be winding down.
“It’s particularly relevant for vaccine hesitance, and maybe taking the flu shot this year can ease some angst about the new COVID-19 vaccine,” says Hofmann, an associate professor of internal medicine and a cardiologist at the Michigan Medicine Frankel Cardiovascular Center. Michigan Medicine is the academic medical center of the University of Michigan.
Researchers reviewed medical charts for more than 27,000 patients who were tested for a COVID-19 infection at Michigan Medicine 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 significant after controlling for other variables including ethnicity, race, gender, age, BMI, smoking status, and many comorbid conditions, Hofmann says.
People who received their flu shot were also significantly less likely to require hospitalization, although the researchers didn’t find a significant difference in mortality between the two groups. No one in the study tested positive for both infections at the same time.
The underlying mechanism behind the association isn’t yet clear, Hofmann says.