The Food and Drug Administration (FDA) has issued emergency use authorizations for updated booster shots for both Moderna and Pfizer/BioNTech's messenger RNA (mRNA) COVID-19 vaccines. Both boosters are bivalent, containing components of the original virus strain and the currently prevalent BA.4 and BA.5 omicron variants. The shots are meant to function solely as boosters. People are eligible for the single bivalent booster shots if it has been at least two months since they have completed primary vaccination or have received a booster dose of the earlier approved vaccines. Moderna is authorized for people over age 18 and Pfizer/BioNTech for those over age 12.
Considering the speed with which the virus has been mutating and the increased infectiousness of the new variants, the FDA is approving COVID-19 booster shots in much the same way that it does seasonal influenza vaccines. Annually updated influenza vaccines do not need to undergo human clinical trials unless the vaccine makers have significantly changed the way they make the vaccines. The same situation applies to the COVID-19 boosters. The mRNA vaccines are essentially plug-and-play, where vaccine makers do not have to reformulate vaccines they already know work, but can instead switch out or add new mRNAs that produce the viral proteins that rev up our immune systems.
Given that the original COVID-19 vaccines and boosters in most cases are still effective against severe disease, some think that booster shots will not add much protection for people who have already been vaccinated or infected. Paul Offit, the director of the Vaccine Education Center at Children's Hospital of Philadelphia, told The Atlantic that he does not plan to get a booster this fall because having been thrice vaccinated and infected. "I think I'm protected against serious illness," he added. Offit was one of the two members of the FDA's vaccine committee to vote against asking vaccine makers to create omicron-specific boosters.
But a recent preprint analysis compared regular booster shots with variant-specific boosters like the new bivalent shots. In that analysis, getting any booster significantly enhances protection against both symptomatic and severe COVID-19 disease with variant-specific boosters providing a modest additional increase in protection. However, one other consideration, suggests University of Rochester respiratory pathogen researcher Angela Branche in Science, is that the broadened immunity that updated vaccines may confer would pay off if new variants emerge.
A better strategy than pursuing a constantly mutating virus with booster shots would be to develop a universal vaccine targeting a wide variety of coronaviruses. Walter Reed Army Institute of Research is expected to report the results of its phase one clinical trial of its pan-coronavirus vaccine candidate soon. In July, a team of vaccine researchers associated with the Francis Crick Institute in London reported in Science Translational Medicine that a vaccine targeting a far more stable protein in coronaviruses immunized mice against a wide array of those viruses.
Disclosure: I have been fully vaccinated (Moderna) and boosted twice (Pfizer). I also had a mild case of COVID-19 earlier this summer that I treated with Paxlovid and I experienced Paxlovid rebound. Nevertheless, I intend to get an updated booster in early October. Everyone should take their own circumstances into account as they update their risk preferences with respect to COVID-19 boosters this fall.