Study Suggests Flu Vaccine Protects Against Severe COVID-19 Infection in Children

Child Getting Vaccinated

According to the Centers for Disease Control and Prevention (CDC), seasonal influenza cases in the U.S. remain lower than usual for this time of year, with most areas experiencing minimal reported activity. While it’s most likely our social distancing, mask wearing and extra sanitizing to thank for this, the flu vaccine still has a role to play this season. 

Researchers from the University of Missouri School of Medicine published their study on the flu vaccine’s impact on COVID-19 pediatric patients. The team found that children who received the seasonal flu shot were less likely to suffer symptoms from COVID-19 infection.  

“It is known that the growth of one virus can be inhibited by a previous viral infection,” said Anjali Patwardhan, M.D., professor of pediatric rheumatology and child health.  

Patwardhan reviewed the records of 905 children who had been diagnosed with COVID-19 from February through August 2020. Those who had received the flu vaccine during flu season had better odds of being asymptomatic and avoiding respiratory issues or severe disease. 

“Research on the pediatric population is critical because children play a significant role in influencing viral transmission,” Patwardhan said. “Understanding the relationship and co-existence of other viruses alongside COVID-19 and knowing the vaccination status of the pediatric patient may help in deploying the right strategies to get the best outcomes.” 

These findings are in alignment with another study done in COVID-19 patients aged 10 and up by Günther Fink, PhD, University of Basel and the Swiss Tropical and Public Health Institute.  

Looking at over 53,000 patients hospitalized in Brazil between January 1 and June 23, 2020, mortality was consistently lower across all age groups in patients who received a flu vaccine in March 2020 or later. Absolute mortality ranged from a risk difference of 12% in patients 10-19 years old to 3% in patients over 90 years old. 

Overall, the study found that those who received the influenza vaccine in 2020 but prior to the onset of the pandemic had 17% lower odds of mortality. Surprisingly, when the vaccine was administered after the onset of COVID-19 symptoms, mortality odds dropped 36%. 

“This phenomenon is called virus interference, and it can occur even when the first virus invader is an inactivated virus, such as the case with the flu vaccine,” Patwardhan said. 

Researchers in both groups also considered other factors that may apply here. For example, smoking is generally more common among those who do not get vaccinated, which could impact COVID-19 disease outcomes. Medical comorbidity actors such as diabetes or obesity were ruled out through the hospital records. 

COVID-19 has disproportionately affected minority communities in our nation and across the world. Patwardhan hypothesized that the higher incidence of COVID-19 in these populations may be linked to their consistently lower vaccination rates, apart from other health inequalities. The study was recently published in the journal Cureus.

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