Pfizer and BioNTech are developing a Covid-19 booster vaccine for the SARS-CoV-2 virus and its circulating mutations, with plans to progress it to the clinic next month.

The booster vaccine is an updated version of the authorised BNT162b2 Covid-19 vaccine and is made to specifically target the entire spike protein of the Delta variant.

In a booster trial that is underway, initial data showed that a booster dose, which is the third dose of BNT162b2, administered six months following the second dose showed an encouraging tolerability profile.

Against the wild type and the Beta variant (B.1.351) of the virus, the vaccine-induced neutralisation titres five to ten-fold greater compared with two initial doses.

Furthermore, data from a study published recently showed that immune sera collected shortly after the second dose had robust neutralisation titers against the Delta variant (B.1.617.2 lineage) in lab tests.

The companies noted that a third dose could potentially increase those antibody titres, comparable to the third dose working against the Beta variant. Preclinical and clinical studies are being carried out to confirm this theory.

On obtaining the necessary data, Pfizer and BioNTech plan to submit it to the US Food and Drug Administration (FDA), the European Medicines Agency (EMA) and other regulatory authorities.

According to the companies, the third dose of BNT162b2 could potentially preserve the increased levels of protective efficacy against all known variants, including Delta.

The first batch of the mRNA required for the clinical trial has been produced at BioNTech’s facility in Mainz, Germany. Subject to regulatory approvals, Pfizer and BioNTech will initiate clinical studies next month.

According to real-world data reported by the Israeli Ministry of Health, vaccine efficacy to prevent infection and symptomatic disease was observed to decline six months after a two-dose vaccination. The vaccine preserved efficacy in preventing serious illness.

This data is in line with an ongoing analysis in the Phase III study conducted by the companies.

In a statement, BioNTech said: “That is why we have said, and we continue to believe that it is likely, based on the totality of the data we have to date, that a third dose may be needed within six to 12 months after full vaccination.”

This May, Pfizer commenced a new study analysing the co-administration of a booster dose of its Covid-19 vaccine followed by its 20-valent pneumococcal conjugate vaccine (20vPnC) candidate in adults aged 65 years and above.