Chief WHO scientist Soumya Swaminathan has cautioned against knee-jerk reactions to early studies that hinted the Pfizer-BioNTech vaccine may have reduced efficacy against the new variant.
She pointed out that the studies done so far were small and that the reduction in the "neutralising activity" varied dramatically between different studies. five fold in some experiments to up to 40-fold in others.
They also only looked at the neutralisation of antibodies, when "we know the immune system is much more complex than that," she said.
"So I think it's premature to conclude that this reduction neutralising activity would result in a significant reduction in vaccine effectiveness," she said. "We do not know that."
The WHO experts stressed the importance of vaccination, highlighting that even if vaccines prove less effective against Omicron, as some data indicates, they are still expected to provide significant protection against severe disease.
WHO emergencies director Michael Ryan so far the data indicates the variant is "efficiently transmitting, and probably more efficiently transmitting even than the Delta variant."
"That does not mean that the virus is unstoppable," he said.
"But it means the virus is more efficient at transmitting between human beings. And therefore we have to redouble our efforts to break those chains of transmission to protect ourselves to protect others."
“If it transmits more rapidly, it could still sicken more people, overburden health systems and more people die," he said.
World Health Organization chief Tedros Adhanom Ghebreyesus also said that emerging data from South Africa suggests increased risk of reinfection with Omicron, but there is also some evidence that Omicron causes milder disease than Delta.
However, more data was needed before drawing firm conclusions, he added.
Worldwide concern is growing over the Omicron variant as it has now spread to 57 countries.
The WHO chief urged countries everywhere to boost their surveillance to help provide a clearer picture of how Omicron is behaving.
Also read: Govt tightens rules for international travellers arriving in India as Omicron threat looms
