Monovalent messenger ribonucleic acid (mRNA) COVID vaccines from Moderna and Pfizer/BioNTech are no longer authorized for use in the US, the US Food and Drug Administration announced 18 April. Instead, the emergency use authorizations (EUAs) for their bivalent vaccines have been amended so they can be updated more easily in the future.

The move includes authorizing the currently available bivalent vaccines for all doses administered to people 6 months of age and older.

At this stage, the data shows that most of the US population 5 years of age and older have antibodies to SARS-CoV-2, the virus that causes COVID-19, as a result of either vaccination or having been infected with the virus, Peter Marks, director of the Center for Biologics Evaluation and Research (CBER), said at a press conference. These data support simplifying the use of the authorized bivalent mRNA COVID-19 vaccines and the agency believes this approach will help us achieve higher vaccination coverage throughout the country.

While the EUAs for the monovalent vaccines are withdrawn, the biologics license application (BLA) for each vaccine remains in effect, according to Marks. He said that similar to how influenza BLAs remain on the market even if they are not used, such products allow manufacturers to use data derived from their use in the supplemental applications filed later with the agency.

FDAs decision to authorize the bivalent vaccines is based on data from the use of monovalent mRNA vaccines against the original SARS-CoV-2 strain and the omicron BA.1 variant, as well as some bivalent trial data. Ultimately, as the vaccines are being updated, the agency says it is relevant to look at the process that was used to develop the monovalent vaccines.

Marks says FDA is comfortable extrapolating the hybrid data from people who have taken the monovalent and bivalent vaccines in clinical trials and real-world evidence.

Ultimately well have additional data for the bivalent [vaccines] but that doesnt mean well leave the monovalent data behind entirely, he added. I think thats useful to help us understand some of the properties of these vaccines.

The decision to update the vaccines follows a 26 January meeting of the FDAs Vaccines and Related Biological Products Advisory Committee (VRBPAC) where the experts unanimously recommended harmonizing the strain composition of COVID-19 vaccines. They also recommended simplifying the vaccine dosing schedule (RELATED: Vaccine adcomm recommends harmonizing COVID-19 shots, Regulatory Focus, 26 January 2023).

The committee will meet again in June to discuss the strain composition of the COVID-19 vaccines for Fall 2023, and industry stakeholders have asked FDA in the past to consider allowing updates to the vaccines based on animal studies to accelerate development.

Animal studies may be important as we move into new variants in the event that we dont have clinical data from humans and we need to make a strain change, said Marks. Were not sure whether that will be the case this year or not yet, but we will obviously always try to rely on the most robust data, which if we have data would be data from humans and well only fall back to using animal data based on what emerges.

This is all because this particular virus seems to evolve very rapidly and we need to do whatever we can to keep up and protect the population, he added.

The updated EUAs mean that most children and adults who have been vaccinated with the monovalent vaccine but who have not gotten a second dose of the bivalent vaccine are eligible to get it. Those who have already received a bivalent vaccine, however, are not eligible to get another dose.

Additionally, most unvaccinated people are eligible for a single dose of a bivalent vaccine, instead of taking multiple doses of the original monovalent mRNA vaccines.

Those who are 65 or older and have already gotten a shot of the bivalent vaccine can get a booster at least four months after their first shot.

People who are immunocompromised, and who have also gotten a preliminary bivalent vaccine, are eligible for a booster two months after the first shot and thereafter can get additional shots at the discretion of their healthcare provider. Children between the ages of 6 months and 4 years who are immunocompromised can get boosters depending on the kind of vaccine they have previously gotten.

FDA said unvaccinated children between the ages of 6 months and 5 years can receive a two-dose series of the Moderna bivalent vaccine. Those between the ages of 6 months and 4 years can receive a three-dose series of the Pfizer-BioNTech bivalent vaccine.

Children who are 5 years of age may receive two doses of the Moderna bivalent vaccine or a single dose of the Pfizer-BioNTech bivalent vaccine, the agency added. Children 6 months through 5 years of age who have received one, two or three doses of a monovalent COVID-19 vaccine may receive a bivalent vaccine, but the number of doses that they receive will depend on the vaccine and their vaccination history.