GENEVA (REUTERS) - Governments need to reassess national responses to Covid-19 and speed up vaccination programmes to tackle Omicron, though it is it too early to say how well existing shots will protect against the new variant, the World Health Organisation (WHO) said on Wednesday (Dec 8).

The variant's global spread suggests it could have a major impact on the Covid-19 pandemic, and the time to contain it is now before more Omicron patients are hospitalised, WHO director-general Tedros Adhanom Ghebreyesus said.

"We call on all countries to increase surveillance, testing and sequencing," he told a media briefing. "... Any complacency now will cost lives."

The WHO noted early evidence from BioNTech and Pfizer of the effectiveness of their vaccine against Omicron.

The German and US companies said on Wednesday a three-shot course of their Covid-19 vaccine was able to neutralise the new Omicron variant in a laboratory test, while two doses resulted in lower neutralising antibodies by a factor of 25.

Warning against jumping to conclusions from the test, the WHO's chief scientist said it was too soon to say whether the reduction in neutralising antibodies meant the shot was less effective.

"We do not know that," Soumya Swaminathan told the briefing, adding that coordinated global research efforts were needed.

The WHO also said it would publish a review of its stance on booster doses within days, but with vaccination rates worryingly low in much of the developing world, administering primary doses - rather than boosters - remained its priority.

"Wholesale boosters are not the solution," Swaminathan said.