COVID-19 shots might be tweaked if variants get worse

LAURAN NEERGAARD

The makers of COVID-19 vaccines are figuring out how to tweak their recipes against worrisome virus mutations — and regulators are looking to flu as a blueprint if and when the shots need an update. “It's not really something you can sort of flip a switch, do overnight,” cautioned Richard Webby, who directs a World Health Organization flu center from St. Jude Children's Research Hospital. Viruses mutate constantly and it takes just the right combination of particular mutations to escape vaccination.