(NEW YORK) — New and updated COVID-19 booster shots were given an emergency use authorization by the Food and Drug Administration Wednesday morning, paving the way for shots in arms as soon as next week.

The booster shots were updated to target two different COVID strains in one shot — the current omicron subvariants, BA.4 and BA.5, which make up 99% of new cases in the U.S., and the original strain of COVID-19.

This is the first time current COVID-19 vaccines have had a major upgrade. In the future, experts expect the vaccines could be updated periodically to match current strains — akin to the way the flu shot is slightly different each year.

Public health officials directed the vaccine companies to create a bivalent vaccine — a vaccine that targets two different strains — in the hopes that the compilation will provide broader protection against COVID this fall and winter, as infections could rise with flu season, the cold weather and more time indoors.

Before the shots are able to be administered to the public, an independent panel of experts at the Centers for Disease Control and Prevention will meet on Thursday to review the data on the booster shots.

If the panel votes in favor of recommending the shots, CDC Director Rochelle Walensky could give the final sign-off within days and shots could be administered after the holiday weekend.

The U.S. government has purchased about 171 million shots, between contracts with Pfizer and Moderna.

Pfizer’s updated vaccine is authorized for people 12 and older, while Moderna’s shot is for people 18 and older. A review of the new boosters for children under 12 is expected soon.

“The COVID-19 vaccines, including boosters, continue to save countless lives and prevent the most serious outcomes (hospitalization and death) of COVID-19,” FDA Commissioner Robert Califf said in a press release on Wednesday morning.

“As we head into fall and begin to spend more time indoors, we strongly encourage anyone who is eligible to consider receiving a booster dose with a bivalent COVID-19 vaccine to provide better protection against currently circulating variants,” he said.

Unlike the original vaccines and boosters, these new shots will not go through a lengthy clinical trial process where thousands of Americans are dosed with the vaccines to test their safety and long-term effectiveness. However, federal health officials stress that these new shots will still be just as safe as the original vaccines because the underlying vaccine platform, mRNA, is the same, and has been through many varying clinical trials.

“We have worked closely with the vaccine manufacturers to ensure the development of these updated boosters was done safely and efficiently. The FDA has extensive experience with strain changes for annual influenza vaccines. We are confident in the evidence supporting these authorizations,” Dr. Peter Marks, director of the FDA’s Center for Biologics Evaluation and Research, said in a statement.

“The public can be assured that a great deal of care has been taken by the FDA to ensure that these bivalent COVID-19 vaccines meet our rigorous safety, effectiveness and manufacturing quality standards for emergency use authorization,” Marks added.

Part of that review was an evaluation of a clinical study of a different updated booster shot that vaccine companies had made during an earlier omicron wave. The clinical trial of that booster shot, which targeted the BA.1 variant and the original strain of COVID, was considered relevant enough to the bivalent vaccines targeting the BA.4 and BA.5 lineages that the FDA found it to be enough to authorize.

Health experts say that the decision not to use time-consuming clinical trials for each new shot is also a strategic move, in an effort to keep vaccines up to date with the rapidly evolving variants — a process that will likely mimic how the flu vaccine is altered each year.

It’s unclear what the demand for new booster shots will be. Across the country, more than half of those eligible to be boosted have yet to do so, according to data from the CDC.

Although the immunity provided by COVID-19 vaccines continues to wane with time, data published by the CDC shows that COVID-19 booster doses are still offering protection against severe forms of disease and death, particularly among older Americans.

Among people ages 50 years and older, the unvaccinated had a risk of dying from COVID-19 that was 14 times higher than their fully vaccinated and double-boosted peers.

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