With 4th COVID-19 vaccine doses looming, experts say not so fast

Even as most eligible Americans have yet to receive their first COVID-19 vaccine boosters, Pfizer and Moderna have now asked the FDA to authorize yet another booster dose -- especially for elderly Americans, a group that tends to have weaker immune protection. Pfizer asked the FDA to authorize fourth doses for people older than 65, while Moderna asked for authorization for everyone 18 and older (though company executives said the greatest need would be among older adults).