BioNTech said it and partner Pfizer may not be able to stick with their plan to launch an omicron-targeting vaccine by the end of March, depending on how much clinical trial data regulators will require.

"Regulatory requirements are currently under discussion with the relevant authorities. Inclusion of clinical trial data in the regulatory filings may have an impact on the delivery of initial batches, currently expected to be ready by end of March," a spokesperson told Reuters on Tuesday.

Pfizer and BioNTech said earlier they started a clinical trial to test a new version of their vaccine specifically designed to target the COVID-19 omicron variant, which has eluded some of the protection provided by the original two-dose vaccine regimen.