U.S. drug regulators on Aug. 31 authorized updated COVID-19 vaccine booster shots despite no clinical trial data being available for the modified formulations.
The U.S. Food and Drug Administration (FDA) granted emergency use authorization to Moderna and Pfizer for the updated boosters.
The original vaccines were based on components of the Wuhan strain of the virus that causes COVID-19. The updated shots contain components of the Wuhan strain and of the BA.4 and BA.5 subvariants of the Omicron variant.
BA.5 is the subvariant currently dominant in the United States.
“The FDA has extensive experience with strain changes for annual influenza vaccines. We are confident in the evidence supporting these authorizations,” Dr. Peter Marks, director of the FDA’s Center for Biologics Evaluation and Research, said in a statement.
Dr. Robert Califf, the FDA’s commissioner, said that the agency was strongly encouraging people to get an updated booster if they’re eligible, “to provide better protection against currently circulating variants.”
The authorizations came just eight days after Moderna requested authorization, and nine days after Pfizer’s request.
Paucity of DataMuch of the data underpinning the requests for authorization were for a different formulation, a combined Wuhan–BA.1 formulation. BA.1 is another subvariant of the Omicron variant. BA.1 hasn’t been dominant in the United States for months.
A phase 2/phase 3 study for Moderna’s Wuhan–BA.1 bivalent vaccine showed that it triggered a stronger antibody response than the booster based solely on the original strain, the company has said. It also appeared to offer protection against the BA.4 and BA. 5 subvariants. Full results of the study have not been released.
Pfizer and its partner BioNTech also said that a phase 2/phase 3 study showed their Wuhan–BA.1 bivalent performed better than the original formulation, and had a “favorable safety profile.” The results of the study haven’t been released apart from a press release.
Moderna and Pfizer also included preclinical data for the shots containing the original strain and components of BA.4 and BA.5 in their applications. Preclinical means that no humans are involved in the testing.
The FDA’s advisory panel in June recommended vaccine makers modify their booster shots to include components of BA.5.
The panel wasn’t convened again before the Aug. 31 decision.
Dr. Vinay Prasad, an epidemiology professor at the University of California–San Francisco, was among the critics of the FDA’s authorizations, saying on Twitter that the lack of human trial data means that authorities were “flying blind.”