Pfizer BioNTech and Moderna logos major COVID-19 vaccine creatorsFDA has authorized bivalent COVID-19 boosters from Moderna (Nasdaq:MRNA) and Pfizer/BioNTech (NYSE:PFE/Nasdaq:BNTX).

The FDA has authorized the updated Moderna vaccine as a single booster dose in individuals at least 18 years old. In addition, the agency authorized the Pfizer/BioNTech vaccine for those at least 12 years old.

Individuals in those age groups who have waited at least two months after receiving a second or third dose of a monovalent COVID-19 vaccine are eligible for the bivalent COVID-19 boosters.

The updated Moderna mRNA-1273.222 and Pfizer/BioNTech BNT162b5 vaccines could be available at U.S. vaccination sites in the coming days.

The updated COVID-19 vaccines encode the spike protein from the original SARS-CoV-2 strain and the BA.4 and BA.5 lineages of the omicron variant.

According to data from Walgreens, the omicron variant is responsible for nearly 100% of COVID-19 infections in the U.S.

Clinical trial data suggested that two doses of the original Pfizer/BioNTech and Moderna vaccines were about 95% effective at protecting against infection. Additionally, a 2021 study found that the former vaccine provided 90% protection against hospitalization for six months.

That study found that vaccine effectiveness against infection steadily dropped from 88% after the first month to 47% after five months.

The mutation of the SARS-CoV-2 virus, however, has chipped away at the vaccine’s effectiveness. According to data from the CDC, two doses of the original mRNA vaccines were about 61% effective at protecting against hospitalization resulting from infection with the BA.1 omicron subvariant.

FDA predicts that the BA.4 and BA.5 lineages of the omicron variant will drive the majority of COVID-19 infections in the U.S. this fall and winter.

The virus’s ability to swiftly mutate, however, has stymied many previous prediction attempts.

The FDA reviewed data from the original monovalent COVID-19 vaccines before authorizing the updated boosters. It also considered safety and immunogenicity data from a clinical trial of a bivalent COVID-19 vaccine that encoded for the BA.1 lineage of omicron.

FDA’s decision to authorize the updated boosters means the original monovalent mRNA COVID-19 vaccines are no longer licensed for use as boosters in individuals 12 and older.

The agency will potentially extend its authorization of the bivalent boosters to include other age groups.

MRNA shares were down 2.53% to $132.49 in early afternoon trading. PFE shares fell 1.18% to $45.31, while BNTX shares dipped 1.13% to $145.42.