FILE - In this Jan. 22, 2021, file photo, empty vials of the Pfizer-BioNTech COVID-19 vaccine are seen at a vaccination center at the University of Nevada, Las Vegas, in Las Vegas.
The makers of COVID-19 vaccines are figuring out how to tweak their recipes against worrisome virus mutations if and when the shots need an update.
The good news: Many of the new COVID-19 vaccines are made with new, flexible technology that’s easy to upgrade.
TESTING VACCINES 2.0First-generation COVID-19 vaccines were tested in tens of thousands of people to be sure they work and are safe — research that took many months.
After all, flu vaccines protect against three or four different types in one shot.