Pfizer Begins Testing COVID-19 Vaccine Targeted to Omicron

Pfizer Inc. announced Tuesday that it has launched a trial that will compare its existing COVID-19 vaccine against a new version tailored to beat back the highly contagious omicron variant.

"While current research and real-world data show that boosters continue to provide a high level of protection against severe disease and hospitalization with omicron, we recognize the need to be prepared in the event this protection wanes over time and to potentially help address omicron and new variants in the future," Kathrin Jansen, senior vice president and head of vaccine research & development at Pfizer, said in a company statement. "Staying vigilant against the virus requires us to identify new approaches for people to maintain a high level of protection, and we believe developing and investigating variant-based vaccines, like this one, are essential in our efforts towards this goal."

The new U.S. study will include up to 1,420 healthy adults, aged 18 to 55 years, and will assess the updated, omicron-targeted vaccine for use as a booster or for primary vaccinations. The modified vaccine's safety and how it bolsters the immune system in comparison to the original vaccine will be examined by the researchers. Volunteers will receive varying vaccine doses and will be monitored for how long virus-fighting antibodies remain at high levels after vaccination, so it could take months for the full study results to be available.

One group of roughly 600 volunteers who received two doses of the original Pfizer vaccine three to six months ago will receive either one or two omicron-based shots as boosters. Another 600 who have already received three doses of the original Pfizer vaccine will be given a fourth dose of either the regular vaccine or the omicron-matched version. The study also will enroll some unvaccinated volunteers who will receive three doses of the omicron-based vaccine.