By Dr. Mallika Marshall

BOSTN (CBS) – There’s another good reason to get an annual flu vaccine. A new study found that people who got a flu shot last season were less likely to get COVID-19 at the beginning of the pandemic.

Researchers at the University of Michigan looked at data on more than 27,000 patients who were tested for COVID-19 between March and July of 2020.

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They found that those who had received a flu shot were more than 20% less likely to test positive for COVID-19. They were also less likely to require hospitalization.

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It’s not clear why.

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Researchers say perhaps people who get flu vaccines are more likely to follow CDC pandemic guidelines, but they say it’s also possible the flu vaccine could have a direct effect on the immune system’s response to the coronavirus.

Dr. Mallika Marshall