Pfizer's booster provides a much stronger immune response against the omicron variant than its two-shot series, according to the results of two recent studies.
The University of Oxford released results from a study testing the COVID-19 vaccines made by Pfizer and AstraZeneca against omicron. The researchers tested blood samples taken from people 28 days after their second dose of either vaccine.
The researchers observed "a substantial fall in neutralization" when omicron was introduced to the blood samples compared to the immune responses elicited by previous variants.
"Importantly, we have not yet assessed the impact of a 'third dose' booster, which we know significantly increases antibody concentrations, and it is likely that this will lead to improved potency against the omicron variant," the researchers wrote.
The findings were published Dec. 13 in preprint server MedRxiv. They have not been peer reviewed.
Israeli researchers from the Sheba Medical Center and Israeli Health Ministry conducted a similar study, and the results will be published soon in the New England Journal of Medicine, The Wall Street Journal reported Dec. 12.
The research team examined blood samples taken from 20 Sheba workers who received a third Pfizer dose at least a month prior and 20 workers who received their second shot five or six months prior but had not received a booster.
The researchers found employees who had received a booster were significantly more likely to neutralize the omicron variant than those who received only two shots.
Both studies echo Pfizer's Dec. 8 news release, in which the drugmaker said its booster provided significant protection against omicron during a laboratory study. Pfizer said the initial vaccination series did not protect against the variant as well as the booster did, suggesting omicron evades antibodies but could be quelled if there are enough in a person's body.