Most people ages 12 and older are considered “up to date” with their COVID-19 vaccines if they received either three doses of the mRNA shots from Pfizer-BioNTech or Moderna, or two doses of Johnson & Johnson’s Janssen vaccine. But some public health experts say another dose might be needed in the coming months.

On March 15, Pfizer and BioNTech requested authorization from the U.S.