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

Pfizer's CEO Albert Bourla previously said at a conference that the pharmaceutical giant could be ready to file for regulatory approval of the shot by March.

The company's head of vaccine research Kathrin Jansen said in a statement that while current data showed that boosters against the original Covid strain continued to protect against severe outcomes with Omicron, the company was acting out of caution.

“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,” she said.