The next round of Covid booster shots should be modified to target the extremely contagious omicron subvariants BA.4 and BA.5, the Food and Drug Administration announced Thursday.
The FDA has asked Pfizer-BioNTech and Moderna to develop so-called bivalent vaccines that are designed to target the original coronavirus strain, as well as the BA.4 and BA.5 subvariants, Dr. Peter Marks, the FDA’s top vaccine regulator, said in a statement.
“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,” Marks said.
The FDA hopes the updated vaccines will be available for an anticipated October booster campaign, according to Marks.
The BA.4 and BA.5 subvariants — considered the most contagious forms of the virus to date — made up about 52% of all new Covid cases in the United States for the week ending June 25, according to the Centers for Disease Control and Prevention. That same week, BA.1, the original omicron variant, made up 0% percent of new cases.
Both Pfizer and Moderna have developed shots that target both the original coronavirus strain and BA.1. Those vaccines upped the immune response to that strain, but appeared to provide less protection against BA.4 and BA.5.
Pfizer told NBC News in a statement that it could have an updated vaccine that targets BA.4 and BA.5 ready to be distributed by the first week of October.
Moderna did not immediately respond to a request for comment, though the company has previously said it is prepared to update its vaccine as needed.
Omicron and its growing family of subvariants have dealt a blow to the effectiveness of Pfizer’s and Moderna’s existing vaccines, which are still in their first iteration, designed to target the original coronavirus strain identified in Wuhan, China, in late 2019.
The federal government is hoping that updating the vaccines to better match circulating strains will improve the shots’ effectiveness and perhaps provide longer-lasting immunity. The approach is similar to the one used for the flu shot, which is updated each year to target the strains scientists predict will be the most predominant.
On Tuesday, the FDA’s vaccine advisory committee overwhelmingly voted in favor of recommending that booster shots include a component that targets the omicron variant.
The panel did not, however, specify which strain or strains of omicron the boosters should target, leaving it up to scientists at the FDA to decide. Many committee members, however, did mention they preferred a vaccine that targeted BA.4 and BA.5.
The companies will be expected to submit new data that shows the BA.4/BA.5 bivalent vaccines trigger an immune response comparable to the existing vaccines and are safe, according to guidance posted on the FDA’s website.