The US must update vaccines against the omicron variant

U.S. regulators told COVID-19 vaccine makers Thursday that fall boosters require modifications to protect against new relatives of the omicron variant.

The Food and Drug Administration said the original vaccines can be used for those receiving the first doses. But now that immunity is easing and the family of super-contagious variants of the omicron family become more adept at dodging protection, the fall reinforcements call for an update.

The recipe consists of combining the vaccines that protect against the BA 4 and BA 5 omicron variants with the original vaccine. These mutations make up more than half of new cases in the United States.

There is no way to tell if a relative of the omicron will be the threat as cold weather approaches in the northern hemisphere or if it will be replaced by a new mutant. And the current vaccines from Pfizer and Moderna continue to provide good protection against the most severe cases of COVID-19 as long as people get the recommended boosters.

But so-called “bivalent” vaccines would allow boosters to retain the proven benefits of the original vaccine while giving it a broader range of protection. It is a common strategy in vaccination. For example, flu shots protect against four strains of influenza and are modified annually based on which one is circulating.

Scientific advisers recommended to the FDA this week that boosters for the fall vaccination campaign contain some version of omicron, but did not say whether it should be the mutant omicron that caused last winter’s spike or the genetically different relatives that replaced it.

Pfizer and Moderna were already developing and testing boosters against the first mutant omicron, anticipating putting them into circulation in October. They found that the additional protection is safe and turned to producing more antibodies against omicron instead of new doses of the current vaccine.