An FDA advisory committee voted Tuesday to recommend changing the composition of COVID-19 booster vaccines to include the addition of the omicron variant of SARS-CoV-2 as a component.
Following a full day of discussions and presentations from WHO, the FDA and vaccine manufacturers, the Vaccines and Related Biological Products Advisory Committee (VRBPAC) voted 19-2 in favor of the change.
“Over the past 2 years, we’ve seen waves of COVID hospitalizations associated with an evolution of the virus and the virus has rapidly evolved through several different variants,” Peter Marks, MD, PhD, director of the FDA’s Center for Biologics Evaluation and Research, said during the meeting.
Marks said that the U.S. has been fortunate to have several vaccines available that have provided protection. However, he noted, their effectiveness has waned over time as well as in response to emerging variants.
Because of this, and because of the potential for more variants to emerge, Marks said it is important to discuss variant-specific vaccine compositions for future booster campaigns.
Evidence in favor of the decision was presented in data from vaccine manufacturers who prepared various modified vaccine candidates containing an omicron variant spike for evaluation in clinical trials.
One study assessing Moderna’s bivalent mRNA vaccine — which includes the original vaccine and a new vaccine targeting the omicron variant — looked at vaccination in previously uninfected subjects who received a second booster of either the original vaccine the candidate vaccine.
The study demonstrated that the bivalent booster produced a non-inferior neutralizing antibody response with a higher neutralizing antibody geometric mean titer. Additionally, the omicron-containing booster had a statistically superior neutralizing antibody response against omicron, with a geometric mean titer of 2,372 (95% CI, 2071, 2718) compared with 1,473 (95% CI, 1271, 1708) for the original vaccine.
Two additional studies presented during the meeting assessed a monovalent omicron mRNA vaccine from Pfizer-BioNTech called BNT162b2 OMI. In one study, patients aged 18 to 55 years, with or without evidence of prior infection, received a second booster of either the companies’ original vaccine or the new candidate vaccine.
In the primary immunogenicity analysis of participants without prior infection, the omicron vaccine had a superior neutralizing antibody response to the omicron variant compared with the prototype booster, with GMT being 1,929 (95% CI, 1632, 2281) and 1,100 (95% CI, 932, 1297), respectively.
Additional data from a second study showed that, among patients 55 years or older, the evaluable immunogenicity analysis of participants without evidence of prior infection, GMT ratios for 30 g and 60 g of monovalent vaccine BNT162b2 OMI (GMT 1,015 and 1,435, respectively) to the 30 g original vaccine (GMT 456) were 2.23 (95% CI, 1.65, 3.00) and 3.15 (95% CI, 2.38, 4.16), respectively.
Overall, experts agree that these data showed that an omicron monovalent vaccines or omicron bivalent vaccines as a second booster vaccination improve neutralizing antibody responses to omicron and do not negatively affect the neutralizing antibody response against the strain of virus that the initial vaccine was originally designed for.
“I voted in favor of omicron booster because I think it’s important to broaden immunity,” Wayne Marasco, MD, PhD, professor in the department of cancer immunology and virology at the Dana-Farber Cancer Institute and professor of medicine at Harvard Medical School, said during the meeting. “We can do better. I’m not sure if the mRNA vaccine as they have been presented so far are giving us the best kind of immunity we can get.”
He added, “I think this is a step in the right direction, but we have to reevaluate this moving forward.”