Pfizer, BioNTech Select COVID-19 Vaccine Candidate, Initiate Phase 2/3 Study

Pfizer and BioNTech have selected a coronavirus disease 2019 (COVID-19) vaccine candidate and have initiated their phase 2/3 safety and efficacy trial.

Following a review of preclinical and clinical data, Pfizer and BioNTech have selected a coronavirus disease 2019 (COVID-19) vaccine candidate and have initiated their phase 2/3 safety and efficacy trial.  

The vaccine candidate, BNT162b2, is a nucleoside-modified messenger RNA (modRNA) vaccine that encodes an optimized severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) full-length spike protein antigen. Among the 4 vaccines being investigated in the BNT162 development program, BNT162b2 emerged as the strongest candidate based on available data demonstrating robust immune response and overall tolerability.

Additionally, in a statement, the Companies noted that “BNT162b2 elicited T cell responses against the receptor binding domain (RBD) and against the remainder of the spike glycoprotein that is not contained in the BNT162b1 vaccine candidate.” This they believe may potentially generate more consistent responses across a diverse population, including older individuals.

The phase 2/3 study is expected to enroll up to 30,000 volunteers between the ages of 18 and 85 years. Individuals will receive BNT162b2 at a 30mcg dose intramuscularly or placebo in a 2 dose regimen 21 days apart. The primary end point of the study will be prevention of COVID-19, with secondary end points being prevention of severe disease and infection by SARS-CoV-2. Approximately 120 trial sites have been chosen, including 39 states in the US; areas with significant SARS-CoV-2 transmission have been prioritized for enrollment.

“The phase 2/3 study protocol follows all the US Food and Drug Administration (FDA) guidance on clinical trial design for COVID-19 vaccine studies,” said Kathrin U. Jansen, PhD, Senior Vice President and Head of Vaccine Research & Development, Pfizer. Recently, the FDA issued guidance to assist in the development and licensure of vaccines for COVID-19. Among the recommendations, was the inclusion of thousands of participants, including those with comorbidities, as well as people with prior SARS-CoV-2 infection, in order to generate sufficient data.

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Based on the findings of this trial, the Companies hope to have enough data to seek Emergency Use Authorization or some form of regulatory approval by October 2020. The vaccine candidate was recently granted Fast Track designation, which allows for expedited review by the FDA.  

Manufacturing efforts are already increasing to keep up with potential demand. If a vaccine is approved, the Companies expect to produce up to 100 million doses by the end of 2020 and possibly more than 1.3 billion doses by the end of 2021.


  1. Pfizer and BioNTech Choose Lead mRNA Vaccine Candidate Against COVID-19 and Commence Pivotal Phase 2/3 Global Study. Published 7/27/20. Accessed 7/28/20.
  2. Study to Describe the Safety, Tolerability, Immunogenicity, and Efficacy of RNA Vaccine Candidates Against COVID-19 in Healthy Adults. Accessed on 7/28/20.