WASHINGTON, July 25 (Reuters) - Top U.S. infectious disease official Anthony Fauci said on Sunday that Americans who are immune compromised may end up needing COVID-19 vaccine booster shots.

"Those who are transplant patients, cancer chemotherapy, auto-immune diseases, that are on immunosuppressant regimens, those are the kind of individuals that if there's going to be a third booster, which might likely happen, would be among first the vulnerable," Fauci said during a CNN interview.

Citing recent studies that show there might be waning immunity in vaccinated people, Fauci said U.S. health officials are reviewing data to determine when boosters might be needed.

“It’s a dynamic situation. It’s a work in progress, it evolves like in so many other areas of the pandemic,” said Fauci, the director of the National Institute of Allergy and Infectious Diseases. “You’ve got to look at the data.”

(Reporting by Linda So; Editing by Tim Ahmann and Grant McCool)