BioNTech and Pfizer's established COVID-19 vaccine will likely offer strong protection against any severe disease from the new omicron virus variant, BioNTech's Chief Executive Uğur Şahin told Reuters, even as the biotech firm protectively makes a bolt for an adapted version of the shot.

Lab tests are currently underway over the next two weeks analyzing the blood of people who had two or three doses of BioNTech's Comirnaty vaccine to see if antibodies found in that blood inactivate omicron.

Şahin told Reuters he expects results to show some loss of vaccine protection against mild and moderate disease due to omicron but the extent of that loss was hard to predict.

BioNTech on Monday said it had started work on a version of its established COVID-19 shot that is tailored to omicron, though it was not yet clear if it was necessary.

Şahin’s words came on the same day Israel announced omicron variant has been detected in two fully-vaccinated doctors Israeli doctors.

The two doctors had received three doses of the Pfizer-BioNtech vaccine, and so far have shown mild COVID-19 symptoms, the hospital said.

The physician who had returned from Britain had probably infected his colleague, officials said.

Two more people have been identified in Israel as carrying the new variant, health officials have confirmed, one of them a tourist from Malawi who had received the AstraZeneca vaccine.

First reported to the World Health Organization in South Africa less than a week ago, the new strain has rapidly spread everywhere from Africa to the Pacific, and from Europe to Canada, causing dozens of countries to announce travel restrictions. While the World Health Organization (WHO) chief Tedros Adhanom Ghebreyesus warned against overreaction to omicron, world markets have already slumped on renewed fears due to the variant.

Forty-two cases of the COVID-19 omicron variant have been confirmed in 10 European Union countries, the head of the EU's public health agency said on Tuesday.

The EU drug regulator said it could approve vaccines adapted to target the omicron variant within three to four months if needed, but that existing shots would continue to provide protection.

Omicron shares several key mutations with two previous variants, beta and gamma, that made them less vulnerable to vaccines. In addition, omicron has 26 unique mutations, many of them in regions targeted by vaccine antibodies.