Responding to the emergence of the omicron variant, Pfizer and BioNTech initially developed a version of their Comirnaty mRNA vaccine to protect against the BA.1 form of the virus. Clinical data shared earlier this year showed the vaccine neutralized BA.4 and BA.5, subvariants that emerged after development of the vaccine began, but to a lesser extent than BA.1.
Recently, the US Food and Drug Administration asked Pfizer and other vaccine developers to work on modified candidates containing a BA.4/BA.5 component. Pfizer plans to ship the BA.1 and BA.4/BA.5 vaccines in the autumn, as CEO Albert Bourla explained on a conference call with investors on July 28.
“Pfizer is well positioned to satisfy its current contractual obligations and potential demand within its production capacity through the end of the year. Because of our robust manufacturing capabilities, we are planning to deliver both variant vaccines in the fall, pending regulatory approvals,” said Bourla.
The FDA is offering the BA.4/BA.5 bivalent vaccine a truncated path to market that could facilitate its use in the autumn booster campaign. To seek emergency use authorization, Pfizer will submit safety and immunogenicity results on the BA.1 vaccine supported by preclinical and chemistry, manufacturing and controls data related to the BA.4/BA.5 candidate.
“This strategy is bolstered by previous experience showing that overall responses have been similar between human clinical and mouse data, our clinical experience with beta and omicron-modified vaccine candidates, and by leveraging our mRNA platform and manufacturing experience for the current vaccine,” said Mikael Dolsten, chief scientific officer at Pfizer.
Dolsten and his colleagues plan to run a clinical trial of the BA.4/BA.5 candidate to support full licensure of the vaccine in the US and other markets. Pfizer was still discussing the design of the study with the FDA at the time of the conference call with investors.
The team is also working on a next-generation vaccine designed to provide durable antibody and T cell immune protection against severe disease and hospitalization for at least one year. Dolsten said Pfizer plans to take “a stepwise approach by designing and testing different candidates that engage multiple arms of the immune system including antibodies and T cells.”