Pfizer and BioNTech have initiated a phase 2 study evaluating a new version of the COVID-19 vaccine that the companies hope will better protect against the virus.
The Pfizer-BioNTech COVID-19 vaccine, BNT162b5, consists of RNAs encoding ‘enhanced’ prefusion spike proteins for the SARS-CoV-2 wild-type strain and an Omicron variant, with the aim of increasing the magnitude and breadth of the immune response.
The vaccine candidate will be evaluated in a US-base study, enrolling around 200 participants aged 18 to 55 who have already received one booster dose at least 90 days prior to their enrolment in the study. The participants will be divided into subgroups based on the number of months since their last dose. The study does not include a placebo.
BNT162b5 is the first of multiple vaccine candidates with an enhanced design, the companies stated, representing their long-term COVID-19 vaccine strategy to overcome the relatively short-lived immune response seen with their first-generation vaccine, BNT162b2.
The trial’s commencement comes as vaccine developers are beginning to develop new versions of their vaccines in response to Omicron, following the US Food and Drug Administration’s (FDA) recommendation to continue developing Omicron-targeting formulations, with the aim of making the vaccines available in autumn this year.
Earlier in July, Pfizer and BioNTech completed a submission to the European Medicines Agency (EMA) for their Omicron-adapted bivalent COVID-19 vaccine, based on the BA.1 sub-lineage, for patients 12 years and older.
The application followed positive results from a phase 2/3 trial, which found that a 30µg booster dose of the Omicron-adapted bivalent vaccine candidate elicited a superior immune response against Omicron BA.1 compared to the companies’ current COVID-19 vaccine.
Moderna also announced positive data in July for its bivalent BA.1 booster candidate, mRNA-1273.214, demonstrating a significantly higher neutralising antibody response against Omicron subvariants BA.4 and BA.5 compared to its currently authorised booster, mRNA-1273, regardless of prior infection status or age.
Moderna is also advancing another bivalent candidate for autumn, but the mRNA-1273.214 bivalent booster is the only candidate expected to have demonstrated significantly higher titers against the BA.4/5 strain in a clinical trial.