Pfizer-BioNTech Covid-19 shot loses power against Omicron variant, but booster restores protection

People who have received two doses of the Pfizer-BioNTech Covid-19 vaccine are likely susceptible to infection from the Omicron variant of the coronavirus, but a third shot restores antibody activity against the virus, the companies said Wednesday.

Their findings are based on lab experiments using the blood of people who have received the vaccine. In a press release, the companies reported a 25-fold reduction on average in the levels of neutralizing antibody activity against the Omicron variant in people who had received two doses of their Covid-19 vaccine. But they also found that blood, or sera, from people who had received boosters “neutralized the Omicron variant to levels that are comparable to those observed” for the original form of the coronavirus that the vaccine was based on, with neutralizing antibody levels increased 25-fold by a third shot.

The results from Pfizer echo those reported on Tuesday by a team of scientists in South Africa.