The Omicron coronavirus variant poses a “very high” global risk, with some evidence that it evades vaccine protection but clinical data on its severity remain limited, the World Health Organisation says.

Considerable uncertainties surround Omicron whose mutations may lead to higher transmissibility and more cases of Covid-19 disease, the WHO said in a technical brief.

“The overall risk related to the new variant of concern Omicron remains very high for a number of reasons,” it said, reiterating its first assessment of Nov 29.

“And second, preliminary evidence suggests potential humoral immune escape against infection and high transmission rates, which could lead to further surges with severe consequences,” the WHO said, referring to the virus' potential ability to evade immunity provided by antibodies.