The Biden administration plans to begin offering next-generation COVID-19 booster shots as soon as the Labor Day weekend, according to people familiar with the matter, aiming to stave off a fall surge in cases of the disease.

Food and Drug Administration regulators are expected to clear the use of COVID-19 vaccines reformulated for omicron variants next week, the people said. They asked not to be identified ahead of an official announcement.

The so-called bivalent vaccines are designed to better protect against subvariants of the virus that are now dominant in the U.S., BA.4 and BA.5. The shots are poised to begin shipping next week and can be administered after Centers for Disease Control and Prevention clearance.

A CDC advisory panel hearing is set for Sept. 1 to 2 to discuss the issue, the people said. CDC Director Rochelle Walensky has the final say and could sign off as soon as next week.

That timeline sets up the potential for a smattering of shots as soon as the Labor Day weekend beginning Sept. 3, with broader availability in the following week or two, the people said. The U.S. will have between 10 and 15 million doses initially available, one of the people said, out of a total order of 171 million doses.

People 12 and up are expected to be eligible for a fresh dose, one of the people said, in line with regulatory proposals by vaccine manufacturers. Nearly 40 million adults under age 50 who already got one booster will then be able to get a second – for some, their first COVID shot in nearly a year.

The administration’s new vaccination push was reported earlier by the New York Times.

The U.S. market for booster shots has been anemic. Only about 27% of American adults under age 50 have sought an extra dose of the vaccines, and only 27% of people age 65 and up – about 15 million – have sought a second booster.

For children, booster uptake has been even lower, with just 4% of kids age 5 to 11 getting a third dose.

That signals demand could remain low for the new round of boosters, and officials privately acknowledge that they don’t expect long lines for vaccines.

Earlier this week, Pfizer Inc. asked U.S. regulators to clear a vaccine that offers protection against the original SARS-CoV-2 virus, which causes COVID-19, as well as the BA.4 and BA.5 subvariants of omicron. The booster hasn’t yet been tested in a clinical trial, though Pfizer and its partner BioNtech SE will launch a study this month.

Moderna Inc. has asked regulators to clear a competing booster shot. Moderna said Friday it’s suing Pfizer and BioNTech, alleging their COVID shots infringe on its patents.

Congress has declined the Biden administration’s requests for more money to buy COVID-19 vaccines and treatments, forcing the administration to reallocate existing funds to buy as much as it could. The 171 million next-generation booster shots the U.S. has already ordered aren’t enough to cover everyone in the U.S. but may meet demand for the time being.

Clearance of the next-generation shots is expected to be paired with expanded eligibility to receive them. Currently, only adults 50 and up and those who are at least moderately immunocompromised are eligible for a second booster. People under 50 who are not immunocompromised are only eligible for one booster.

About 262 million people in the U.S. have had at least one dose, while 108 million have gotten at least one booster shot and 21 million have gotten two, CDC data show.