Pfizer Inc. and BioNTech SE announced the publication of new results from two laboratory studies demonstrating that three doses of the Pfizer-BioNTech COVID-19 Vaccine (BNT162b2) elicited antibodies that neutralize the Omicron variant (B.1.1.529).
Data published in the peer-reviewed journal Science, includes readouts of sera data from 51 vaccinated individuals that received two or three doses of BNT162b2 as well as a study evaluating the neutralization potential of serum antibodies from a subset of vaccinated individuals against the live virus. Both data sets confirm previously announced initial study results demonstrating that serum antibodies induced by BNT162b2 neutralize the SARS-CoV-2 Omicron variant after immunization with three doses.
In comparison, sera from individuals who received two doses of the COVID-19 vaccine revealed limited neutralization titers against the Omicron variant in both data sets, indicating that two doses of BNT162b2 may not be sufficient to protect against infection with the new variant.
However, based on observations that around 85% of epitopes in the spike protein recognized by CD8+ T cells are not affected by the mutations in the Omicron variant, the companies believe two doses may still induce protection against severe disease.
Separately, data from a live virus laboratory study conducted with the University of Texas Medical Branch (UTMB) that support and further extend these findings were posted on the preprint server bioRxiv. Sera taken 1-month following a third dose showed a 22-fold increase in neutralization titers against Omicron compared to titers just prior to the third dose (7.9 to 8.8 months after second dose), suggesting more robust protection against the new variant may be achieved with the current COVID-19 vaccine series plus a booster dose.
Additionally, the neutralizing titer levels against Omicron after immunization with three doses were similar to antibody titer levels after two doses against wild-type and other variants that emerged before Omicron. Further, from 1 to 4 months after a third dose, neutralization titers against wild-type and Omicron decreased by 1.6 and 2.0 times, respectively, suggesting similar waning for both variants. All sera effectively neutralized Omicron at 4 months following a third dose.