Jen Christensen, CNN

Your COVID-19 booster in the fall will likely look a little different going forward.

The U.S. Food and Drug Administration decided Thursday to advise manufacturers that when they update the COVID-19 vaccine booster they should add an Omicron BA.4/5 component to the current vaccine mix. This would create what's known as a bivalent, or two component, booster.

"We have advised manufacturers seeking to update their COVID-19 vaccines that they should develop modified vaccines that add an omicron BA.4/5 spike protein component to the current vaccine composition to create a two component (bivalent) booster vaccine, so that the modified vaccines can potentially be used starting in early to mid-fall 2022," Dr. Peter Marks, director of the FDA's Center for Biologics Evaluation and Research, said Thursday in a statement.

Independent advisers to the FDA met on Tuesday and the Vaccines and Related Biological Products Advisory Committee voted to support recommending inclusion of an Omicron-specific component for a COVID-19 booster.

The committee felt that a modified vaccine would offer broader protection to match the coronavirus strains that are in circulation now. The committee was not asked to vote on what sublineage to include or whether the booster should be monovalent vaccine or a bivalent vaccine, which would include two strains.

Two Omicron subvariants, BA.4 and BA.5, are now dominating transmission of COVID-19 in the United States, according to the U.S. Centers for Disease Control and Prevention. The levels of neutralizing antibodies that a previous infection or vaccinations elicit are several times lower against these subvariants compared with the original coronavirus, studies suggest. This means while the current vaccines still provide substantial protection against severe disease, these subvariants could likely lead to surges of new infections.

Marks said Tuesday that there will be a conversation going forward to determine who needs another booster and what that booster will look like.

The FDA said in May that the "new normal" may include an annual COVID-19 and flu shot for people in the fall. Cases are expected to rise again in the fall and winter.

Figuring out what goes in the next vaccines are a tricky decision, because as Dr. Arnold Monto, the acting chair of the independent vaccine advisers committee, suggested, this is a virus that changes quickly and puts scientists in "uncharted territory"

"Looking in the past doesn't help us a great deal to look in the future for this virus which has baffled a lot of us and made predictions almost irrelevant," Monto added.

The FDA said Thursday that this coming year is what it considers a "transitional period." It has not advised manufacturers to change the primary vaccination for those who still have not gotten the COVID-19 vaccine. The FDA said that the primary series of shots that use the formula created to fight the version of the virus that first emerged in 2019 still provides a base of protection against serious COVID-19 symptoms, even with the version of the virus that is currently in circulation.

The new formulation would instead go into a booster shot that may be introduced in the fall.

Vaccine makers have already been testing new versions of their vaccines and presented the data at the independent advisers meeting on Tuesday.

Moderna's presented details about its bivalent booster vaccine candidate that contains components of both Moderna's original COVID-19 vaccine and a vaccine that targets the original Omicron variant.

VaccineFDA advisers to consider whether omicron-specific coronavirus vaccines are needed
While it isn't specifically designed to target BA.4/5, the company said its booster known as mRNA-1273.214 demonstrates a "potent neutralizing antibody response" against these subvariants.

Pfizer/BioNTech also presented data to the committee that showed that their two COVID-19 vaccine boosters targeting Omicron showed a substantially higher immune response than its current COVID-19 vaccine. Preliminary lab studies suggest the vaccines could also neutralize the Omicron BA.4 and BA.5.

"Based on the strength of our initial data from our Omicron BA.1 bivalent candidates, we believe we have a strong solution with a bivalent BA.4/BA.5 subvariant booster as we head into this next chapter of the pandemic, and will continue to share our available data with health experts and regulators. We are ready to distribute a vaccine to the world by early October 2022, pending regulatory authorizations," said a Pfizer spokesperson in a statement to CNN.

Another vaccine maker, Novavax, has committee support for emergency use authorization in the United States, but the FDA has not yet authorized its vaccine. Novavax told the committee that it has been developing variant-specific updated versions of its COVID-19 vaccine as well as a COVID-19 and flu combination vaccine.

On Thursday, the FDA encouraged the vaccine makers to submit the latest data on these modified vaccines to the FDA for evaluation prior to the authorization of an Omicron BA.4/5 component vaccine.

The FDA also said it would ask vaccine makers to begin clinical trials with modified vaccines with the Omicron BA.4/5 component, because the agency said the data would be helpful as the pandemic "further evolves."

At Tuesday's meeting, the World Health Organization told the FDA's independent committee that the vaccination strategy going forward should probably be based around a vaccine that would offer as broad a kind of protection as possible, rather than just continuing with the vaccines that were made against the original strain that is no longer in circulation.

"I still think there's value in increasing the breath of immunity and I will reiterate that we're not trying to match what may circulate," said Dr. Kanta Subbarao with the World Health Organization Collaborating Center for Reference and Research on Influenza and the University of Melbourne. "It is not so much to match what is likely to circulate because there's so much uncertainty about the trajectory of this evolution."