Public health experts say COVID-19 cases are anticipated to spike again this fall, but new vaccine versions expected to be released soon will target subvariants that dominate cases in the United States.

These updated vaccines to be available as a single-dose booster sometime after Labor Day are termed “bivalent” vaccines, meaning they work by stimulating an immune response against two different antigens.

The Food and Drug Administration and the Centers for Disease Control and Prevention are anticipated to authorize and recommend the Pfizer bivalent vaccine as a booster for those age 12 and older and the Moderna version for those 18 years and older. However, per the FDA, the bivalent vaccines will not be able to be administered as a primary series.

The new COVID-19 bivalent booster combines the original strain with the Omicron subvariants BA.4 and BA.5 and will be distributed under FDA Emergency Use Authorization (EUA). Pfizer and Moderna applied for EUAs for their bivalent products on Aug. 22 and Aug. 23, respectively.

The BA.4 and BA.5 subvariants account for more than three-quarters of COVID-19 infections in the country. The subvariants also account for the majority of cases worldwide, according to the CDC.

The FDA and CDC decisions are expected to occur prior to or just after the Labor Day holiday, said Air Force Col. Tonya Rans, chief of the Defense Health Agency Immunization Health Division.

Pfizer and Moderna anticipate quickly shipping their messenger RNA (mRNA) bivalent vaccines in September pending authorization.

Since the bivalent vaccines will be issued under emergency use authorization, getting this booster shot is not required, but highly recommended.

For Military Health System beneficiaries, the Department of Defense does not currently mandate booster shots, but does require that service members and other beneficiaries must have first received a primary series from one of the available vaccines before getting the bivalent booster.

Will I Be Able to Find a Bivalent Shot?

Military medical treatment facilities are pre-ordering the new vaccines, and there is not a supply issue anticipated, Rans noted. The Department of Health and Human Services has secured more than 171 million doses of the bivalent boosters for distribution.

CDC has not yet decided what the minimum interval between your most recent COVID-19 vaccine shot and the new bivalent booster will be. “However, we expect a decision soon after a CDC meeting on September 1 or 2,” Rans said.

The CDC published a chart that shows the schedule for primary series and boosters and clinical considerations for four FDA authorized or approved vaccines, including the latest authorized from Novavax. That vaccine received EUA only as a two-shot primary series for those 12 and older.

Novavax cannot be administered as a booster dose at this time.

All current COVID-19 vaccine booster doses are available under an EUA. The primary doses of Pfizer and Moderna’s vaccines have full FDA approval, while Johnson & Johnson/Janssen and Novavax are available as an EUA.

The Johnson & Johnson/Janssen vaccine should only be used in “very limited situations for primary and booster vaccinations,” CDC said.

Authorized in December 2020, the original vaccines were designed to protect against serious consequences of the COVID-19 pandemic that began in March 2020. Those shots and then boosters also protect against the Delta variant that began circulating in June 2021 as well as the Omicron B.1 variant, which began showing up in November 2021.

The BA.4 and BA.5 subvariants evolved from the Omicron mutation in early 2022. They are more contagious and can bypass the immunity you may have developed from a past infection or vaccination, according to federal experts.

Bivalent Shots and Flu

The availability of the new bivalent boosters will coincide with the traditional influenza vaccination season. A COVID-19 booster and the flu vaccine can be given at the same time, Rans emphasized.

DOD will begin shipping the 2022-2023 influenza vaccines right after Labor Day, she said. DOD expects HHS to begin shipping the Pfizer and Moderna bivalent boosters around the same time, pending authorization.

The flu is expected to show a resurgence this year after two slower seasons, and the infection season is expected to start earlier, federal experts have predicted.

The FDA is not requiring new studies in humans for the bivalent vaccines to receive an EUA, but will use data already gathered from the Delta and Omicron BA.1 variant studies and public health vaccination data.

The agency has directed that there will be new clinical studies on the BA.4 and BA.5 boosters from manufacturers that will be reviewed at a later date to see if the results can support full FDA approval.

The FDA’s Dr. Peter Marks, who has vaccine oversight at the agency, said he expects “this coming year to be a transitional period” for COVID-19.