Preliminary laboratory studies demonstrate that three doses of the Pfizer-BioNTech COVID-19 vaccine neutralize the Omicron variant, while two doses appear to be significantly less effective, Pfizer said in a statement on Wednesday. The ability of a vaccine to protect against infection can be examined in two ways: in the laboratory to see if antibodies found in the blood of vaccinated individuals neutralize the variant, or by collecting data from the field to show how many vaccinated individuals become infected compared with unvaccinated individuals. The company’s scientists compared the results from blood taken from individuals who had received the booster a month earlier with those from blood from vaccinees with only two shots. Pfizer said that the level of protection offered by the booster against Omicron resulted similarly to the one provided by two doses of the vaccine against other variants. The research showed that the immunity offered by the third dose against Omicron was 25-times higher than the immunity offered by two doses. According to the statement, two doses likely still offer some protection against severe disease. “Our preliminary, first dataset indicates that a third dose could still offer a sufficient level of protection from disease of any severity caused by the Omicron variant,” said BioNTech CEO Ugur Sahin. “Although two doses of the vaccine may still offer protection against severe disease caused by the Omicron strain, it’s clear from these preliminary data that protection is improved with a third dose of our vaccine,” said Pfizer CEO Albert Bourla. “Ensuring as many people as possible are fully vaccinated with the first two dose series and a booster remains the best course of action to prevent the spread of COVID-19.” However, at least one researcher said that Pfizer’s statements about the vaccine’s effectiveness must be taken with caution.
“It must be said honestly that currently Pfizer statements are based on in vitro experiments and in order to evaluate the effectiveness of the Omicron vaccine we will have to wait patiently to gather information from the real world,” said Dr. Oren Kobiler of Tel Aviv University. “Right now everything is speculation based on lab data.”
He added that in addition, there is concern that an updated and adapted vaccine to target the Omicron variant, which Pfizer said it could have ready by March, might be less effective against the Delta variant. The latter is still the most dominant strain in most of the world and “therefore it is unclear whether it is right to rush into further developments at this stage,” Kobiler said. Pfizer said that they will continue to collect both data from laboratory tests and from the field to obtain more information. Antibodies represent only one part of the immune system and therefore laboratory tests do not fully mirror the ability of the body to fight a disease. Earlier in the day, the research head of a laboratory at the Africa Health Research Institute in South Africa said that the Omicron variant can partially evade protection from two doses of Pfizer vaccine. Alex Sigal, a professor at the research institute, said on Twitter there was “a very large drop” in the neutralization of the Omicron variant relative to an earlier strain of COVID-19. But the study showed that blood from people who had received two doses of the vaccine and had a prior infection was mostly able to neutralize the variant, suggesting that booster doses of the vaccine could help to fend off infection.