https://apnews.com/c0b2253cf5adc1458d895acbf2f5a8e8 > 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.