LOS ANGELES, Aug. 27 (Xinhua) -- The U.S. Food and Drug Administration (FDA) has approved updated COVID-19 vaccines but significantly restricted their use for many Americans.

"FDA has now issued marketing authorization for those at higher risk: Moderna (6 months and older), Pfizer (5 years and older) and Novavax (12 years and older)," U.S. Health and Human Services Secretary Robert F. Kennedy Jr. said Wednesday in a post on the social platform X.

"These vaccines are available for all patients who choose them after consulting with their doctors," he added.

Kennedy said the FDA has achieved four goals: ending COVID vaccine mandates; keeping vaccines available to people who want them, especially the vulnerable; demanding placebo-controlled trials from companies; and ending the emergency use authorizations (EUAs).

EUAs for COVID-19 vaccines have now been rescinded, according to Kennedy.

Public health experts warned the narrower approval could create uncertainty for Americans not classified as high-risk but still seeking updated vaccines. The move may also make it harder for infants and young children to get vaccinated, despite their vulnerability to severe illness.

Some medical groups, including the American Academy of Pediatrics, have voiced opposition, arguing that the restrictions could prevent families who want to protect their children from accessing the shots.