Pfizer's updated vaccine candidates, a monovalent and a bivalent option, both delivered a "substantially higher immune response" against omicron compared to its current version among study participants 56 and older when used as a fourth booster dose.
In a phase 2/3 study, the monovalent vaccine targeting omicron resulted in a 13.5-times increase in neutralizing antibody titers with 30 micrograms and a 19.6-times increase with 60 micrograms. The bivalent vaccine, which targeted omicron and the original coronavirus strain, proved a 9.1- and 10.9-times increase, respectively, at the 30 and 60 microgram levels.
"Based on these data, we believe we have two very strong omicron-adapted candidates that elicit a substantially higher immune response against omicron than we've seen to date," Pfizer CEO Albert Bourla, PhD, said in a June 25 press release.
The research shows a stronger response against omicron's BA.1 strain compared to "sister variants" BA.4 and BA.5.
The FDA is set to meet June 28 to discuss COVID-19 vaccine research, which will include Pfizer's data on its updated vaccine.
Other companies, including Moderna and Sanofi-GSK, are aiming to tackle the omicron variant with their own vaccine candidates.