However, those immunized before 1968 with an ineffective measles vaccine made from “killed” virus - or people who don’t know which type they got - should be revaccinated with at least one dose, the agency said.
Measles is popping up in U.S. Here's the way to avoid one of the world's most contagious viruses
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University of Texas Medical Branch said that the vaccine remained effective against a mutation called N501Y from new variants found in the U.K. and South Africa.
Some COVID-19 mutations may dampen vaccine effectiveness
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