Three doses of Pfizer-BioNTech vaccine protects against Omicron: Study

According to the companies’ preliminary data, a third dose provides a similar level of neutralizing antibodies to Omicron as is observed after two doses against wild-type and other variants that emerged before Omicron

Pfizer and BioNTech announced results from an initial laboratory study demonstrating that serum antibodies induced by the Pfizer-BioNTech Covid-19 vaccine neutralize the SARS-CoV-2 Omicron variant after three doses. Sera obtained from vaccines one month after receiving the booster vaccination (third dose of Pfizer-BioNTech) neutralized the Omicron variant to levels that are comparable to those observed for the wild-type SARS-CoV-2 spike protein after two doses.

Sera from individuals who received two doses of the current Covid-19 vaccine did exhibit, on average, more than a 25-fold reduction in neutralization titers against the Omicron variant compared to wild-type, indicating that two doses of the vaccine may not be sufficient to protect against infection with the Omicron variant. However, as the vast majority of epitopes targeted by vaccine-induced T cells are not affected by the mutations in Omicron, the companies believe that vaccinated individuals may still be protected against severe forms of the disease and are closely monitoring real-world effectiveness against Omicron, globally.

More robust protection may be achieved by a third dose as data from additional studies of the companies indicate that a booster with the current Covid-19 vaccine from Pfizer and BioNTech increases the antibody titers by 25-fold. According to the companies’ preliminary data, a third dose provides a similar level of neutralizing antibodies to Omicron as is observed after two doses against wild-type and other variants that emerged before Omicron. These antibody levels are associated with high efficacy against both the wild-type virus and these variants. A third dose also strongly increases CD8+ T cell levels against multiple spike protein epitopes which are considered to correlate with the protection against severe disease. Compared to the wild-type virus, the vast majority of these epitopes remain unchanged in the Omicron spike variant.