The US Food and Drug Administration is making it a high priority, the official said.
The US Centers for Disease Control and Prevention reports that the BA.4 and BA.5 subvariants constitute more than 70% of new infections in the country. But while these subvariants may partially escape the immunity produced by the vaccine and by prior infection, vaccination still likely protects against severe illness.
It remains unclear how many American adults would get a second booster dose if one is authorized. As of Thursday, about half of Americans 18 and up who were eligible for a first booster had gotten it, according to the CDC. Just over a quarter of eligible adults 50 and over have gotten a second booster.
Those with a history of Covid-19 infection had a similarly limited response. The authors say this suggests that there may be a ceiling or maximum response that can come with a fourth vaccine dose.
This story has been updated with additional information Monday.