Covid vaccines should still protect people from the worst effects of the new Omicron variant, a senior World Health Organization scientist has said.
WHO emergencies director Dr Mike Ryan said it is "highly unlikely" that Omicron will completely evade vaccine protections.
In an interview with AFP news agency, the WHO's second in command said existing Covid vaccines had been successful against other variants, and he expects jabs to be effective against Omicron too.
"We have highly effective vaccines that have proved effective against all the variants so far, in terms of severe disease and hospitalisation. There's no reason to expect that it wouldn't be so [for Omicron]".
Dr Ryan added that early data suggests Omicron is less severe than other Covid variants, though earlier this week Boris Johnson warned ministers the variant is "more transmissible".
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The WHO's comments follow a study on Omicron and vaccine efficiency in South Africa.
Based on a small sample, and not yet peer reviewed, researchers in the study suggested that the Pfizer vaccine was less effective against Omicron compared to other Covid variants.
Health Secretary Sajid Javid told Parliament on Monday that we don’t yet have a "complete picture" of whether Omicron causes more severe disease or how it interacts with the vaccine.
"We can’t say for certain whether Omicron has the potential to knock us off our road to recovery", he said.
Mr Javid said 10,000 vaccinators would be recruited to bolster the booster programme, and 350 military personnel would be deployed in England to help give boosters, as well as more than 100 in Scotland.
At least 440 Omicron cases had been confirmed in the UK as of Tuesday - 333 in England, 99 in Scotland, five in Wales and three in Northern Ireland.