Existing vaccines will still protect people who contract the Omicron variant from severe Covid-19 cases, according to a top World Health Organization (WHO) official.

"We have highly effective vaccines that have proved effective against all the variants so far, in terms of severe disease and hospitalisation, and there's no reason to expect that it wouldn't be so for Omicron,” Dr Mike Ryan, the WHO's emergencies director, told AFP news agency.

His observation comes at a time when the first lab tests of the heavily mutated new variant in South Africa suggest it can partially evade the Pfizer vaccine.

Researchers say there was a "very large drop" in how well the vaccine's antibodies neutralised the new strain.

But Ryan said there was no sign Omicron would be better at evading vaccines than other variants.

He also said that initial data suggested that the COVID-19 symptoms in the case of Omicron were less severe than the Delta and other strains.

Scientists believe previous infection, followed by vaccination or a booster, is likely to increase the neutralisation level and will probably protect people against severe disease.

More data on how well the Pfizer vaccine works against Omicron is expected to be released in the coming days.

There is no significant data yet on how the Moderna, Johnson & Johnson and other jabs hold up against the new variant.

Dr Anthony Fauci, the top US infectious diseases expert, said early evidence suggests Omicron could be more transmissible but less severe.

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