Preliminary laboratory data suggest that 2 doses of the Pfizer-BioNTech COVID-19 vaccine may not be sufficient to protect against infection with the SARS-CoV-2 Omicron (B.1.1.529) variant. 

The laboratory study was conducted to evaluate the effectiveness of the Pfizer-BioNTech COVID-19 vaccine against the Omicron variant using sera obtained from individuals who received two or three 30mcg doses of the current vaccine. The sera were collected from individuals 3 weeks after receiving the second dose or 1 month after receiving the third dose of the Pfizer-BioNTech COVID-19 vaccine.

Findings demonstrated a 25-fold increase in neutralizing antibody titers in individuals who received the third dose, providing a similar level of neutralization against Omicron as was observed after 2 doses against the wild-type strain. “Although 2 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 Albert Bourla, Chairman and CEO, Pfizer.

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A third dose of the vaccine also increased CD8+ T cell levels against multiple spike protein epitopes, correlating with protection against severe disease. The vast majority of these epitopes (~80%) remained unchanged in the Omicron spike variant when compared with the wild-type virus.

The Companies will continue to collect more data and evaluate real-world effectiveness to assess and confirm protection against Omicron. An Omicron-specific COVID-19 vaccine is currently being developed in the event that it is needed and may be available by March 2022. Data from previous clinical trials evaluating variant specific vaccines will also be submitted to regulatory agencies in order to speed up the process of adapting the vaccine and gaining authorization or approval.


Pfizer and BioNTech provide update on Omicron variant. News release. Pfizer Inc. and BioNTech SE. Accessed December 8, 2021.

This article originally appeared on MPR