Tuesday, 30 March 2021

Americans who got flu shots last year were 25% less likely to test positive for COVID-19 as the disease surged across the country, study finds

 Americans who received flu shots last year were significant less likely to test positive for COVID-19, a new study suggests.

Researchers found that those vaccinated against influenza were 25 percent less at-risk of contracting the virus that causes the illness, known as SARS-CoV-2. 

What's more, those who did later become infected with coronavirus had fewer complications if they had been immunized against the flu.

Scientists aren't yet sure whether the shot itself is protective, or if a person who gets a flu vaccine is simply also more likely to take precautions to protect themself against coronavirus, like mask-wearing and hand-washing. 

The team, from Michigan Medicine, says the findings provide evidence for why the general public should get the flu shot if they haven't already, despite the fact that the U.S. is nearing the end of the 2020-21 flu season may be winding down. 

A new study found that, of the 13,000 Michigan Medicine patients who received the flu shot, 4% contracted coronavirus compared to 5% of the 14,000 patients who did not get the flu shot (file image)

A new study found that, of the 13,000 Michigan Medicine patients who received the flu shot, 4% contracted coronavirus compared to 5% of the 14,000 patients who did not get the flu shot (file image)

COVID-19 patients who were vaccinated against the flu were 40% less likely to be hospitalized and 100% less likely to need mechanical ventilation (above)

COVID-19 patients who were vaccinated against the flu were 40% less likely to be hospitalized and 100% less likely to need mechanical ventilation (above)

Senior author Dr Marion Hofmann Bowman, an associate professor of internal medicine at Michigan Medicine, said one of the inspirations behind the study was misinformation she had seen connecting the flu vaccine to COVID-19 infection.

Despite several prominent media outlets debunking this claim, she said she wanted to address vaccine hesitancy.  

'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,' she said.

'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.' 

For the study, published in the American Journal of Infection Control, the team looked at medical charts for more than 27,000 patients who has tested positive between March 2020 and mid-July 2020.


Researchers looked at flu shot status and controlled for other factors such as age, race, sex and pre-existing conditions. 

Of the nearly 13,000 patients who had received a flu shot in the previous year, four percent tested positive for COVID-19. 

Comparatively, five percent of the 14,000 patients who didn't get a flu shot contracted coronavirus - a difference of 25 percent. 

Next, the researchers looked at the difference in clinical outcomes between COVID-19 patients with the influenza vaccine and those without it,

Patients vaccinated against influenza were 40 percent less likely to be hospitalized and half as likely to need mechanical ventilation.


The length of stay in the hospital was also reduced with coronavirus patients who had gotten the flu shot in the hospital for an average of 12 days compared to an average of 16 days for patients who had not gotten the flu shot.

However, there was no difference in death rates between the two groups of patients.

Hofman says the nature of the link between flu shots and COVID-19 illness or its severity.  

'It is possible that patients who receive their flu vaccine are also people who are practicing more social distancing and following CDC guidelines,' she said.

'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 SARS-CoV-2 virus.' 

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