Covid-19 booster shots modified to protect against the omicron variant are on their way. The FDA has authorized updated versions of the messenger RNA vaccines from Moderna and partners Pfizer and BioNTech.

The announcement Wednesday amends the booster shot section of the emergency use authorizations, permitting a single dose of the new booster at least two months after a person has received the primary vaccination or a previous booster shot. The updated boosters are bivalent. In addition to protecting against the original SARS-CoV-2 strain, they also include components that protect against the BA.4 and BA.5 lineages of omicron. These versions of the virus, which have mutations that make them highly transmissible, are the ones currently driving Covid-19 cases in the U.S. The FDA said these lineages are also predicted to drive cases this fall and winter.

“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,” FDA Commissioner Robert Califf said in the agency’s announcement.

The bivalent Moderna booster is authorized for immunizing those 18 and older. Authorization of Pfizer and BioNTech’s bivalent booster covers individuals age 12 and older. With the changes announced by FDA, anyone age 12 and older may no longer receive a monovalent mRNA vaccines as a booster. The FDA said it will evaluate the use of bivalent boosters in other age groups as it receives supporting data and submissions from vaccine makers.

The FDA authorized the new bivalent boosters without clinical data for versions of the shots designed to protect against the BA.4 and BA.5 subvariants. Pfizer and BioNTech have clinical data for a bivalent vaccine that protects against the original strain and the BA.1 subvariant. In June, an FDA advisory committee voted to recommend that vaccine makers incorporate an omicron component for their booster shots.

Following the advisory vote, the FDA issued guidance to vaccine makers instructing them to incorporate a BA.4 and BA.5 component in their bivalent vaccines in order to address the omicron subvariants that have become dominant in the U.S. The agency added that clinical data for bivalent shots designed to address BA.1 would be enough to seek authorization for shots designed to protect against BA.4 and BA.5. Last week, Pfizer and BioNTech, as well as Moderna, completed their respective bivalent booster submissions to the FDA.

FDA authorization of the bivalent boosters comes one day ahead of a scheduled meeting of an vaccines practices advisory committee to the Centers for Disease Control and Prevention. The agenda includes discussion of both bivalent booster shots, followed by a committee vote. Afterward, CDC Director Rochelle Wolensky may sign off on the updated boosters, which would clear the way for them to become available early next week.

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