population is not immune to SARS-CoV-2 and variants may cause this portion of the population that is not immune to increase," said Adam MacNeil, an epidemiologist at the Centers for Disease Control and Prevention.
To reach the threshold of herd immunity while battling new, more contagious virus strains, a higher proportion of the population needs to get vaccinated, MacNeil said at a Food and Drug Administration meeting reviewing Johnson & Johnson's application to authorize its Covid-19 vaccine for emergency use.