A study from researchers at the University of Pennsylvania has found that the season flu vaccines are a mismatch against the strain of the virus currently in circulation.
"From our lab-based studies, it looks like a major mismatch," Scott Hensley, a professor of microbiology at the University of Pennsylvania who led the study, told CNN.
Hensley said flu season could be worse than usual because measures to reduce the spread of COVID-19 also reduced to spread of the flu virus, lowering the "infection-induced population immunity over the past two years."
"Population immunity against influenza viruses is likely low since these viruses have not circulated widely during the COVID-19 pandemic," the researchers explained in their pre-print study. "Social distancing, mask-wearing, and decreases in international travel have likely contributed to reduced global circulation of influenza viruses. Once COVID-19-related restrictions are eased or lifted, it is possible that influenza viruses will circulate widely due to lack of infection-induced population immunity over the past two years."
While the flu vaccines may not fully protect against the current strain of the flu virus, Hensley said the vaccines can still protect against severe infections that lead to hospitalizations or death.
"Studies have clearly shown that seasonal influenza vaccines consistently prevent hospitalizations and deaths, even in years where there are large antigenic mismatches," the researchers said.