Two recent studies showed that the updated bivalent boosters were not more effective at targeting newer subvariants than the original formula, but the director of the FDA's vaccine division said these studies have limitations, CNBC reported Oct. 28.
In separate studies, Harvard University and Columbia University researchers tested the tweaked vaccines and the original shots among about 20 people, and the results indicated that Pfizer's and Moderna's new boosters are as effective against subvariant BA.5 as the older vaccines.
"It is important to note that even the data from these initial small studies indicate that the bivalent vaccines are generally at least as good or better as the original vaccines in generating an immune response particularly to BA.4/BA.5 and other newer variants," Center for Biologics Evaluation and Research Director Peter Marks, MD, PhD, said in a statement.
Both of the studies are preprints, and the Columbia researchers concluded that follow-up studies are needed to determine whether "antibody responses will deviate in time, including the impact of a second bivalent booster."
White House COVID-19 response coordinator Ashish Jha, MD, also responded to the small studies and said upcoming larger trials are expected to confirm the safety and efficacy of the bivalent boosters.