Pfizer and BioNTech have begun an evaluation of the safety and immunogenicity of a third dose of the Pfizer-BioNTech COVID-19 vaccine (BNT162b2) to understand the effect of a booster on immunity against COVID-19 caused by the circulating and potential newly emerging SARS-CoV-2 variants.
The study will draw upon participants from the Phase 1 study in the United States who will be offered the opportunity to receive a 30 µg booster of the current vaccine 6 to 12 months after receiving their initial two-dose regimen, states Pfizer in a press release. The study is part of the companies’ clinical development strategy to determine the effectiveness of a third dose against evolving variants.
Evaluate a variant-specific vaccine having a modified mRNA sequence
Separately, in order to be prepared for any potential future strain changes, Pfizer and BioNTech are in ongoing discussions with regulatory authorities, including the U.S. Food and Drug Administration (FDA) and the European Medicines Agency, regarding a registration-enabling clinical study to evaluate a variant-specific vaccine having a modified mRNA sequence.
This study would use a new construct of the Pfizer-BioNTech vaccine based on the B.1.351 lineage, first identified in South Africa. This could position the companies to update the current vaccine quickly if the need arises to protect against COVID-19 from circulating strains, they state. In alignment with the updated guidance issued by the FDA regarding emergency use of vaccines to prevent COVID-19 which provides recommendations for evaluatinga modified vaccine to address variants, the companies are hoping to pursue the validation of future modified mRNA vaccines with a regulatory pathway similar to what is currently in place for flu vaccines.
“While we have not seen any evidence that the circulating variants result in a loss of protection provided by our vaccine, we are taking multiple steps to act decisively and be ready in case a strain becomes resistant to the protection afforded by the vaccine. This booster study is critical to understanding the safety of a third dose and immunity against circulating strains,” says Albert Bourla, Chairman and Chief Executive Officer, Pfizer. “At the same time, we are making the right investments and engaging in the appropriate conversations with regulators to help position us to potentially develop and seek authorization for an updated mRNA vaccine or booster if needed.”
Evaluate the safety and tolerability of a third vaccination irrespective of the level of antibody titers of the trial participant
Administering a third dose will provide an early assessment of the safety of a third dose of BNT162b2, as well as its immunogenicity. This study will evaluate up to 144 Phase 1 participants in two age cohorts, 18-55 and 65-85 years of age. The study will include trial participants who received the two doses in the Phase 1 study 6 to 12 months ago in order to assess the boostability of BNT162b2. Thus, the study will evaluate the safety and tolerability of a third vaccination irrespective of the level of antibody titers of the trial participant. Participants will be assessed at the time they receive the third dose, then one week and one month after, and Pfizer and BioNTech plan to study the ability of the sera from those participants to neutralize SARS-CoV-2 strains of interest. The participants will continue being followed in the study for up to 2 years as originally planned.