Pfizer is expected to ask the Food and Drug Administration to authorize its Covid-19 vaccine booster shot for Americans ages 16 and 17, news outlets reported Monday, as public health experts track the coronavirus’ new omicron variant.

The report comes less than two weeks after the FDA updated its emergency use authorizations for Pfizer and Moderna’s Covid-19 vaccines to make all adults eligible for boosters six months after they take their initial shots.

Health officials are pushing more Americans to get boosters amid concerns about the coronavirus’ new omicron variant, which was first detected by South African scientists last week and has prompted the United States to restrict travel from several countries in southern Africa. President Joe Biden said Monday the omicron variant is “a cause for concern, not a cause for panic,” and that the United States would not resort to lockdowns in response to the variant, but would continue to rely on vaccinations and testing. Dr. Anthony Fauci told CNN Monday it is too early to determine the severity of the variant, though some experts are concerned it could be more transmissible than previous forms of the coronavirus.

The Vaccines and Related Biological Products Advisory Committee, the FDA’s vaccine advisory board, initially voted against recommending Pfizer’s Covid-19 booster for all Americans ages 16 and older in September, citing a lack of evidence that the third shot is safe and necessary for lower-risk patients. The committee instead endorsed booster shots for seniors and high-risk adults.