Pfizer and BioNTech have announced the commencement of a clinical trial of an Omicron-based Covid-19 vaccine candidate in healthy adults aged 18 to 55 years. 

First subjects who were enrolled into the trial have received the vaccine as the initial two-dose regimen and as a booster shot.

The trial will analyse the tolerability, safety and immunogenicity of the vaccine and will enrol up to 1,420 subjects across three cohorts.

Varying regimens of the Pfizer-BioNTech Covid-19 vaccine or an Omicron-based vaccine will be evaluated in these three cohorts.

The latest study intends to address the Omicron variant of the SARS-CoV-2 virus and decide on the potential requirement for variant-based vaccines.

Cohort 1 of the trial will have 615 subjects who were administered two doses of the Pfizer-BioNTech Covid-19 vaccine 90-180 days before enrolment.

Furthermore, the subjects will be administered one or two doses of the Omicron-based vaccine.

Cohort 2 will have 600 subjects who have already received three doses of the Pfizer-BioNTech Covid-19 vaccine 90-180 days before enrolment.

These subjects will be given a single dose of the Pfizer-BioNTech Covid-19 vaccine or the Omicron-based vaccine.

Nearly 205 vaccine-naïve subjects will be enrolled in cohort 3 of the trial and will be given three Omicron-based vaccine doses.

Pfizer Vaccine Research & Development senior vice-president and head Kathrin Jansen said: “While current research and real-world data show that boosters continue to provide a high level of protection against severe disease and hospitalisation with Omicron, we recognise the need to be prepared in the event this protection wanes over time and to potentially help address Omicron and new variants in the future. 

“Staying vigilant against the virus requires us to identify new approaches for people to maintain a high level of protection, and we believe developing and investigating variant-based vaccines, like this one, are essential in our efforts towards this goal.”

Last week, the Health Ministry of Japan approved the Covid-19 vaccine co-developed by Pfizer and BioNTech for use in children aged five to 11 years.