As the coronavirus assumes contagious new forms around the world, two drugmakers reported on Monday that their vaccines, while still effective, offer less protection against one variant and began revising plans to turn back an evolving pathogen that has killed more than 2 million people.
The news from Moderna and Pfizer-BioNTech underscored a realization by scientists that the virus is changing more quickly than once thought, and may well continue to develop in ways that help it elude the vaccines being deployed worldwide.
The announcements arrived even as U.S. President Joe Biden banned travel to the United States from South Africa beginning Saturday, in hopes of stanching the spread of one variant. And Merck, a leading drug company, on Monday abandoned two experimental coronavirus vaccines altogether, saying they did not produce a strong enough immune response against the original version of the virus.
Moderna and Pfizer-BioNTech both said their vaccines were effective against new variants of the coronavirus discovered in Britain and South Africa. But they are slightly less protective against the variant in South Africa, which may be more adept at dodging antibodies in the bloodstream.