Data needed to determine the advisability of booster shots of the Moderna and Johnson & Johnson Covid-19 vaccines is just weeks away, President Joe Biden's chief medical adviser, Dr. Anthony Fauci, said on Sunday.

Health officials signaled they expected boosters would ultimately be recommended for a broad swath of the population, but urged Americans not to seek booster doses until they have FDA approval.

"We recommend that people wait until you get to the point where you fall into the category where it's recommended," he told CNN.

On Friday, a Food and Drug Administration advisory panel recommended a third shot of the two-dose Pfizer/BioNTech vaccine for people age 65 and older or at high risk of severe Covid-19, but declined to endorse boosters for the wider population.

Though the FDA is not bound by the panel's recommendation, it will take it into consideration when deciding whether to recommend a third round of shots.

"This is not the end of the story," Fauci told CNN's "State of the Union" program. "They're going to continue to look at this, literally in real time," Fauci added.

People who have received the two-dose Moderna vaccine or one-dose J&J vaccine are still awaiting guidance on possible booster shots.

"The actual data that we'll get (on) that third shot for the Moderna and second shot for the J&J is literally a couple to a few weeks away," Fauci told NBC's "Meet the Press" program.

"We're working on that right now to get the data to the FDA so they can examine it and make a determination about the boosters for those people," Fauci added.

More data may also show a broader need for booster shots across the general US population, Fauci said.

The United States leads the world in total reported Covid-19 cases and deaths. Nearly 676,000 people have died during the pandemic in the United States, figures compiled by Reuters showed. An increase in US cases and deaths in recent months has been most acute in areas with lower vaccination rates even as federal health officials implore vaccine holdouts to get their shots.

Biden announced in August the government's intention to roll out booster shots for people age 16 and older, pending approval by the FDA and Centers for Disease Control and Prevention experts.

The FDA's decision-making process does not negate the White House's position favoring boosters, Fauci said, saying the plan was always contingent on FDA's regulatory process.

Dr. Francis Collins, director of the US National Institutes of Health, said on the "Fox News Sunday" program that he expects it would "become clear over the next few weeks that administration of boosters may need to be enlarged," citing existing data from the United States and Israel indicating waning vaccine effectiveness over time.

The officials also signaled the timeline for vaccine authorization for children from 5-11 years old is in the coming weeks.

"For kids 5 to 11, the data is supposed to come in at the end of this month, and FDA will be working 24-7 to go through it," Collins said. "So we all hope that can happen in weeks, and not months."