Monday, September 12, 2022

COVID bivalent booster vaccines ("updated boosters") roll out across the US

 - Jennifer Middleton, MD, MPH

On August 31, the United States (US) Food and Drug Administration (FDA) authorized Pfizer and Moderna's new bivalent COVID booster vaccines, also described as "updated boosters." The FDA amended  Emergency Use Authorizations to authorize the Pfizer and Moderna bivalent vaccines for persons aged 12 years and older and 18 years and older, respectively. The bivalent vaccines "add Omicron BA.4 and BA.5 spike protein components to the current vaccine composition, helping to restore protection that has waned since previous vaccination by targeting variants that are more transmissible and immune-evading." Bivalent/ updated booster vaccines are anticipated to be available later this fall for younger ages

Although Pfizer and Moderna ran trials in humans earlier this year with a bivalent vaccine designed to protect against both the original SARS-CoV-2 strain and the B.1 subvariant, the FDA asked both companies to switch their strategy to targeting the B.A.4/5 subvariants this spring. To fast track their vaccines and hopefully get them approved before the virus can mutate again, the FDA approved the use of data from mouse models only instead of waiting for further human trials:

Regulators [relied] on those results, along with the human neutralizing antibody data from the BA.1 bivalent booster studies, to decide whether to authorize the boosters....The companies will continue to gather more data from human studies; those results probably won't be available until late October or early November.

The FDA emphasized that this strategy has been used successfully for many years to update annual influenza vaccination components and emphasized that they "'have worked closely with the vaccine manufacturers to ensure the development of these updated boosters was done safely and efficiently.'"

Persons who have not yet received their primary COVID vaccinations need to complete that series prior to receiving the bivalent/updated booster; the bivalent/updated boosters "come in booster-sized doses" and "contain less vaccine than the primary series." For persons eligible for a COVID vaccine booster, the EUA recommends only the use of the bivalent/updated booster vaccines going forward. They also recommend a minimum of 2 months' time between the final dose of the primary series and/or last monovalent booster prior to receiving the bivalent/updated booster. Persons recovering from recent COVID-19 infection may "consider waiting a minimum of 3 months."  Some infectious disease experts, though, are recommending longer intervals:

An advisory panel to the C.D.C. voted to recommend the same interval between doses, although several members voiced concerns that two months was too short. Doctors and immunologists said that in general, people should wait around four to six months after immunization or infection. "That’s because your body will probably not generate much of an immune response so soon after a previous encounter with the virus," Aubree Gordon, an epidemiologist at the University of Michigan, said. “Your immunity level is so high that you’ll just neutralize immediately the antigen that’s being produced — you kind of reach a ceiling."

The CDC has given the green light to co-administering the bivalent/updated booster with influenza and/or any other indicated vaccinations; injection sites should be separated by a minimum of 1 inch

The CDC encourages all eligible persons for the bivalent/updated booster to receive it to protect against severe illness, long COVID, and the risk of transmitting the disease to those more vulnerable. If your office or care site won't be stocking it, the website provides a tool to search for COVID-19 vaccine providers by zip code. The AFP By Topic on COVID-19 will continue to be regularly updated, and this recent AFP Curbside Consultation on "Vaccine Disagreement Between Parents" provides guidance regarding vaccine hesitancy.