The good news: Many of the new COVID-19 vaccines are made with new, flexible technology that’s easy to upgrade. What’s harder: Deciding whether the virus has mutated enough that it’s time to modify vaccines — and what changes to make.
“When do you pull the trigger?” asked Norman Baylor, a former Food and Drug Administration vaccine chief. “This is a moving target right now.”
The WHO and FDA are looking to the global flu vaccine system in deciding how to handle similar decisions about COVID-19 shots.
Influenza mutates much faster than the coronavirus, and flu shots have to be adjusted just about every year. National centers around the globe collect circulating flu viruses and track how they’re evolving. They send samples to WHO-designated labs for more sophisticated “antigenic” testing to determine vaccine strength. The WHO and regulators then agree on the year’s vaccine recipe, and manufacturers get to work.