The monovalent messenger RNA Covid-19 vaccines are going away and older adults, as well as those with compromised immune systems, may now get a second booster with one of the authorized bivalent vaccines.

Those changes are part of FDA amendments to the emergency use authorizations of the mRNA Covid-19 vaccines from both Moderna and partners Pfizer and BioNTech. In announcing the amendments Tuesday, the agency said it aims to simplify the vaccine schedule for most people. The updated vaccines—bivalent boosters that address the original SARS-CoV-2 strain and the circulating omicron variants—are now authorized for all doses administered to those age 6 months and older. That change applies to a first-time shot for the unvaccinated or a booster for someone who previously received a monovalent dose. The monovalent mRNA vaccines are no longer authorized for use in the U.S., the agency said.

Speaking on a conference call with journalists on Tuesday, Peter Marks, director of the FDA’s Center for Biologics Evaluation and Research, said available data show that most of the U.S. population age 5 and older have some antibodies to SARs-CoV-2, either from vaccination or by infection. Those antibodies serve as a foundation for protection by the bivalent vaccines.

The revised authorizations follow a January vaccines advisory committee meeting that led to a unanimous vote recommending alignment of the strain composition of Covid-19 vaccines in the U.S. The committee also supported simplifying the vaccine dosing schedule.

Those who aren’t 65 and older or immunocompromised are not eligible for a second booster shot, at least not yet. The FDA said it will discuss future vaccinations for this cohort and others after receiving recommendations from another advisory committee meeting planned for June. That meeting will discuss the composition of the vaccines and whether changes need to be made by the coming fall to address changes in the circulating variants. Marks said this approach sets up Covid-19 vaccination to emulate the practice of annual influenza vaccination.

“SARS-CoV-2 is not the influenza virus, but that said, we’re using that public health model where we’ll look to do our best to select what we believe to be likely to circulate the following fall, winter season, and use that in the vaccine composition to try to protect as many people during the season in which respiratory viruses tend to wreak their havoc,” he said.

Novavax was the last company to receive authorization for a Covid-19 vaccine booster, a decision handed out last October. But that shot was based on the original strain of the virus. The company has said it will deliver an updated vaccine following FDA guidance on a strain change. Marks said the FDA will discuss the matter with Novavax, adding that the company’s vaccine will also be part of the June advisory committee meeting.

The decision to permit a second booster for older adults and immunocompromised people comes later than similar policy changes already made in other countries. The U.K., for example, announced at the beginning of March that a spring booster would become available to people 75 and older, residents of care homes for the elderly, and immunocompromised individuals age 5 and older.

Marks said the FDA decision took longer because the agency needed time to review data supporting use of a second bivalent vaccine in the authorized groups. He added that he hopes this change encourages those who haven’t received a booster to consider getting one. Citing Centers for Disease Control and Prevention data, Marks said only 42% of those eligible for a Covid-19 booster have received one.

The FDA’s amendments to the Covid-19 vaccines will now go to the CDC’s advisory committee meeting on immunization practices, where they will be discussed during a meeting scheduled for Wednesday.

Photo: peterschreiber.media, Getty Images