PFIZER and BioNTech have begun enrolment for a clinical trial to test the safety and immune response of their Omicron-specific Covid-19 vaccine in adults aged up to 55, said the companies in a statement today.

Pfizer CEO Albert Bourla previously said the pharmaceutical giant is likely ready to file for regulatory approval of the shot by March.

Its vaccine research head, Kathrin Jansen, said while data shows that boosters against the original Covid-19 strain continue to protect against severe outcomes with Omicron, the company is acting out of caution.

“We recognise the need to be prepared in the event this protection wanes over time and potentially help address Omicron and new variants in future.”

BioNTech CEO Ugur Sahin said the protection of the original vaccine against mild and moderate Covid-19 appears to wane more rapidly against Omicron.

“This study is part of our science-based approach to develop a variant-based vaccine that achieves a similar level of protection against Omicron as it did with earlier variants, but with longer duration of protection.”

The trial will involve 1,420 people aged between 18 and 55.

It does not include above-55s as the goal of the study is to examine the immune response of participants dosed, rather than estimate vaccine efficacy, said a spokesman from Pfizer.

The trial is taking place across the United States and South Africa, and the first participant was dosed in North Carolina.

The volunteers are split into three groups.

The first involves people who previously received two doses of the current Pfizer-BioNTech vaccine 90-180 days prior to enrolment, and will receive one or two doses of the Omicron vaccine.

The second involves people who received three doses of the current vaccine 90-180 days prior to enrolment, and will receive either another dose of the original shot or an Omicron-specific one.

The third and final group are people who have never previously received a Covid-19 vaccine, and will receive three doses of the Omicron-specific vaccine.

The Pfizer-BioNTech vaccine is the first coronavirus shot to be authorised in the West, in December 2020. It is relatively easy to update to reflect the genetic code of new variants as it is based on messenger RNA technology.

Several countries have started to emerge from their latest waves driven by Omicron, the most transmissible strain to date, though global new cases are still rising.

The coronavirus has killed some 5.6 million people since the outbreak emerged in China in December 2019. – AFP, January 25, 2022.