- Researchers recently identified lower COVID-19 rates among people who received flu shots.
- The odds of testing positive for SARS-CoV-2 were 24% lower for those who received a flu shot compared with those who did not.
- People who had been vaccinated against the flu who tested positive for SARS-CoV-2 had a lower hospitalization rate than people who had not been vaccinated against the flu.
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Since the World Health Organization (WHO) declared COVID-19 a global pandemic, scientists have focused on finding ways to slow down the spread and minimize the severity of medical issues associated with the disease.
Scientists have now developed multiple vaccines and found treatments to improve outcomes.
One group of researchers has been looking back to the earlier months of the pandemic. They noticed that people who had been vaccinated against the flu developed COVID-19 at lower rates and experienced less severe symptoms than people who had not been vaccinated.
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Something that medical professionals have continually emphasized since the onset of the current pandemic is that COVID-19 and the flu are not the same illness.
Although the illnesses may share a few similar symptoms — such as cough, fever, and fatigue — different viruses cause them.
The flu is caused by an influenza virus, of which there are numerous strains. Typically, there are one or two dominant strains per flu season, which scientists attempt to target with a vaccine.
COVID-19, on the other hand, is caused by a coronavirus called SARS-CoV-2.
Not only do these viruses function differently from each other, but SARS-Cov-2 is also far deadlier than the typical flu virus.
Over the past year, scientists have focused on developing a vaccine that helps prevent contracting and spreading SARS-CoV-2. At the same time, researchers have started to explore whether other vaccines, targeting different pathogens, might influence the virus.
Research by scientists at Michigan Medicine at the University of Michigan in Ann Arbor suggests that people who receive a flu vaccine may be less likely to get COVID-19.
Dr. Marion Hofmann Bowman, an associate professor of internal medicine and a cardiologist at Michigan Medicine, is a senior author of the new paper, which appears in the American Journal of Infection Control.
Dr. Hofmann believes that there is a connection between people who get their flu vaccination and a reduction in COVID-19 cases.
“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.”
– Dr. Marion Hofmann Bowman
The group reviewed medical records from more than 27,000 people who took COVID-19 tests at Michigan Medicine. The study included people who underwent testing between February 27 and July 15, 2020.
Of the individuals who underwent testing for COVID-19, almost 13,000 received flu vaccines and just over 14,000 did not.
The number of people who tested positive for SARS-CoV-2 was higher among people who did not get the flu shot. Almost 5% of these participants tested positive for SARS-CoV-2. Of those who did get a flu shot, 4% tested positive for SARS-CoV-2.
According to the paper, “The odds of testing positive for [SARS-CoV-2] was reduced in [people] who received an influenza vaccine compared [with] those who did not by 24%.”
Additionally, people who had been vaccinated against the flu had better outcomes than people who had not been vaccinated.
Those who had not been vaccinated required hospitalization at higher rates than those who had. People who had not been vaccinated were also more likely to need mechanical ventilation and extended hospital stays.
The death rate was about the same between the two groups.
“Recent data [have] also suggested an association between influenza vaccination and reduced mortality from COVID-19 as well as a decreased need for intensive care treatment and invasive respiratory support,” write the authors.
The study authors are not yet sure why people who had been vaccinated against the flu fared better than people who had not been vaccinated against it.
“It is possible that [people] who receive their flu vaccine are also people who are practicing more [physical] distancing and following [Centers for Disease Control and Prevention] guidelines,” suggests Dr. Hofmann.
Dr. Hofmann also says that the reduction in positive SARS-CoV-2 tests could be attributable to “a direct biological effect of the flu vaccine on the immune system relevant for the fight against SARS-CoV-2 virus.”
Even though the researchers may not know exactly why the relationship between flu shots and COVID-19 exists, one thing is clear. They write, “The results of our study indicate that influenza vaccination presents no harmful effect on COVID-19 susceptibility or increased disease severity.”
This is important to ensure that the public does not have any fear of getting vaccinated against the flu. It is important to keep flu numbers down and avoid depleting resources needed to fight COVID-19.
“Instead of a concerning connection between COVID-19 and the flu shot, our publication provides more confidence that getting [the] flu shot is associated with staying out of the hospital for COVID-19,” concludes Dr. Hofmann.
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