Johnson & Johnson's single-dose coronavirus vaccine may be less effective against some variant strains of the virus.
The drugmaker said today its vaccine showed 66% effectiveness overall in protecting against COVID-19. In late-stage trials, the vaccine was 72% effective in the U.S., but only 57% in South Africa. It proved 66% effective in Latin America. Johnson & Johnson is expected to ask the FDA for emergency use authorization as soon as next week.