Pfizer says three doses effective against Omicron

Two doses of the BioNTech and Pfizer coronavirus vaccine may not be enough to protect against the Omicron strain, the companies warned Wednesday, but they stressed it was ‘still effective’ after a third jab.

The companies’ news was called reassuring by experts and came as the first independent data from labs around the world emerged, suggesting that the new variant is better at evading vaccine-trained immunity than those before it.

In preliminary results published on Wednesday, Pfizer and BioNTech said their vaccine is still effective in preventing COVID-19, also against Omicron, if it has been administered three times.

But they warned that the Omicron variant is probably not sufficiently neutralized after two doses.

According to early laboratory research using blood serum from vaccinated people, a booster third dose generated around the same level of antibodies against Omicron as is seen after a second dose with the initial strain.

Blood samples from around 20 people who had received two doses of the current vaccine showed on average a 25-fold reduction in neutralizing antibodies compared to the early strain of the virus, the companies said.

But they added that another part of the immune response - from T cells - were probably still effective against the variant, adding that vaccinated individuals may still be protected against severe forms of the disease. Their results have not been peer-reviewed.

ARR