SOON after vaccination began in many countries, reports of faster-spreading coronavirus variants triggered fears that vaccines might not protect against them. The good news is that initial studies suggest that the existing shots will still work, although they might be slightly less effective against two variants, one that emerged in South Africa and one from Brazil.

“I am optimistic that current vaccines will remain quite useful,” says Jesse Bloom at the Fred Hutchinson Cancer Research Center in Seattle. “But I do expect that eventually it …