The companies tested a vaccine that targets the bivalent and subvariant booster of Omicron BA.1, which targets two strains, which includes the current Pfizer / BioNTech Covid-19 vaccine, and a candidate vaccine that targets Omicron.
The study looked at two different dose levels: 30 micrograms and 60 micrograms in more than 1,200 adults aged 56 years or older. The current primary and booster dose for this age group is 30 micrograms.
The study showed that, at both dose levels, a fourth booster with candidates for the Omicron-modified vaccine resulted in a substantially higher immune response against the variant. One month after injection, the monovalent vaccine showed a 13.5- and 19.6-fold increase in dose-dependent Omicron antibodies. The bivalent vaccine showed an increase in antibodies of 9.1 and 10.9-fold.
Preliminary results from laboratory studies also suggest that vaccines could neutralize Omicron BA.4 and BA.5, the companies said. The BA.4 and the BA. 5 subvariants are increasingly circulating in the United States.
Both vaccine candidates appeared to be safe and well tolerated.
The results were shared in a press release and have not yet been peer-reviewed or published.
“Based on these data, we believe we have two very strong candidates modified by Omicron that elicit a substantially higher immune response against Omicron than we have seen so far,” said Pfizer President and CEO Albert Bourla. in a press release.
Earlier this month, Moderna reported that its Covid-19 bivalent vaccine booster containing an Omicron-targeted vaccine showed a stronger immune response against the variant. The company said its updated reinforcement also showed a “powerful” response against the BA.4 and BA.5 subvariants. The companies will present their data on Tuesday, when the U.S. Food and Drug Administration’s Related Vaccines and Related Products Advisory Committee meets to vote. on updated coronavirus vaccines for the fall.