Flu Vaccine Linked to Less Severe COVID cases

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New research has found evidence of the flu vaccine causing reduced numbers and less severe COVID cases.

In the past, a plethora of false information has come forward regarding the novel coronavirus. One that gained a lot of attention was the claim that the flu vaccine causes coronavirus infection. Despite being outrageous, the false claim led to huge support for anti-vaxxers. However, researchers were soon able to provide scientific evidence disregarding the claim. Now, a team of scientists at Michigan Medicine have found evidence for a positive relationship between the flu vaccine and fewer COVID cases.

Instead of a concerning connection between COVID-19 and the flu shot, our publication provides more confidence that getting your flu shot is associated with staying out of the hospital for COVID-19.

Marion Hofmann Bowman, M.D, senior author

The researchers looked at over 27,000 patients who had undergone COVID-19 testing between March and July 2020. They aimed to compare the difference in positive tests among those who received a flu vaccine a year before, and those who did not. Other than positive tests, they also assessed for severity of the disease, need for hospitalization, mortality, and mechanical ventilation. Results of the study are available in the American Journal of Infection Control.

24% Less Chance of Getting COVID

The findings revealed that those who received a flu vaccine last season had a reduced chance of testing positive for COVID-19. Moreover, those who did test positive, despite the flu shot, had a less severe COVID case.

Out of the approximate 13,000 patients who had received a flu shot, only 4% tested positive for coronavirus. On the other hand, out of the 14,000 that did not receive a flu shot, 4.9% tested positive. Despite controlling for variables such as race, BMI, smoking status, comorbid conditions, gender, and age, the difference remained significant. Furthermore, those who received a flu shot had a less severe infection, fewer rates of hospitalization, and a decreased need for intensive care treatment.

It is possible that patients who receive their flu vaccine are also people who are practising 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.

Marion Hofmann Bowman, M.D, senior author

It is unclear as to what is the underlying mechanism for the association. However, researchers believe that urging people to get vaccinated can help reduce the burden of disease during this pandemic. Therefore, they call for further educating patients on the benefits of the flu vaccine and its widespread promotion.


Anna Conlon, Carmel Ashur, Laraine Washer, Kim A. Eagle, Marion A. Hofmann Bowman. Impact of the influenza vaccine on COVID-19 infection rates and severity. American Journal of Infection Control, 2021; DOI: 10.1016/j.ajic.2021.02.012


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