FDA: Omicron-specific boosters must target new strains

New COVID-19 booster shots should be tailored to target omicron’s BA.4 and BA.5 subvariants as well as the original strain in order to give people the broadest possible protection, U.S. regulators advised drugmakers on Thursday.

The announcement from the Food and Drug Administration (FDA) comes two days after an agency advisory panel recommended tailoring booster shots to target the omicron variant for a fall vaccination campaign.

The BA.4 and BA.5 subvariants now account for the majority of new infections in the U.S., according to the Centers for Disease Control and Prevention. 

It’s possible those variants will be eclipsed in the fall by an even more immune-resistant strain, but the hope is that even if the vaccines target old variants they will provide broad protection against anything new.

The purpose of a “bivalent” shot is to take the protection offered by the initial vaccine and then add to it by including the BA.4 and BA.5 spike protein.

According to the FDA, currently available vaccines have helped reduce the most serious outcomes caused by COVID-19, but the effectiveness of primary vaccination wanes over time against certain variants, including omicron. The first booster doses helped restore that protection, but the effectiveness is also waning. 

The Biden administration needs to give drug makers enough time to develop and adapt the new booster in time for the fall and winter, which is why they made the decision in June.

For example, Moderna told FDA’s advisory committee that it will take until late October or early November to create a vaccine targeting the BA.4 and BA.5 subvariants. 

“As we move into the fall and winter, it is critical that we have safe and effective vaccine boosters that can provide protection against circulating and emerging variants to prevent the most severe consequences of COVID-19,” Peter Marks, FDA’s top vaccine regulator, said in a statement. 

Still, uptake of even a first booster dose has been lagging, an indication that not everyone will want an updated booster this fall.  

The newly formatted shots will only be used as boosters and the initial vaccination will not change, “since a primary series with the FDA-authorized and approved COVID-19 vaccines provides a base of protection against serious outcomes of COVID-19 caused by circulating strains of SARS-CoV-2,” the agency said. 

The Biden administration on Wednesday announced a $3.2 billion contract with Pfizer for 105 million doses of an updated COVID-19 vaccine for a fall campaign. The shot is expected to target the omicron variant. The new doses are expected to begin to be delivered “as soon as late summer 2022 and continue into the fourth quarter of this year,” Pfizer said.

Pfizer has already reported some success with a bivalent vaccine targeting the spike protein of the omicron BA.1 variant, but it’s not clear how long it would take to develop one for the BA.4 and BA.5.