The Centers for Disease Control and Prevention estimates at least 1 million people who got the Pfizer or Moderna coronavirus vaccines have gone back for a third, unauthorized booster shot.

ABC News reported on the findings Tuesday, citing an internal CDC briefing. According to the documents, roughly 1.1 million people are believed to have sought out an extra shot of either two-dose vaccine.

Florida had the most instances of people seeking an extra shot, followed by Ohio, California, Illinois and Tennessee.

The data did not track those who may have gotten an additional dose of the single-shot Johnson & Johnson vaccine. 

It's unclear whether those who got the shot did so at the recommendation of a doctor. The FDA has not authorized a booster shot for any of the vaccines currently available, though booster shots for the immunocompromised may be recommended in the coming weeks.