GENEVA: The Omicron variant of Covid-19 is dangerous -- and especially so for those who have not been vaccinated against the disease, the World Health Organization said Wednesday.

The WHO said the huge global spike in cases was being driven by Omicron but insisted there should be no surrender to the variant of concern.

"While Omicron causes less severe disease than Delta, it remains a dangerous virus, particularly for those who are unvaccinated," WHO chief Tedros Adhanom Ghebreyesus told a press conference.

"We mustn't allow this virus a free ride or wave the white flag, especially when so many people around the remain unvaccinated.

"In Africa, over 85 percent of people are yet to receive a single dose of vaccine. We can't end the acute phase of the pandemic unless we close this gap."

Tedros wanted every country to have 10 percent of their population vaccinated by the end of September 2021, 40 percent by the end of December, and 70 percent by mid-2022.

But 90 countries had still not reached 40 percent, 36 of them still short of the 10-percent mark, he said.

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The "overwhelming majority" of people admitted to hospitals around the world were unvaccinated, he added.

While vaccines remain very effective at preventing death and severe Covid-19 disease, they do not fully prevent transmission, said Tedros.

"More transmission means more hospitalisations, more deaths, more people off work -- including teachers and health workers -- and more risk of another variant emerging that is even more transmissible and more deadly than Omicron."

Tedros said that the numbers of deaths worldwide had stabilised at around 50,000 per week.

"Learning to live with this virus does not mean we can, or should, accept this number of deaths," he said.

WHO emergencies director Michael Ryan added: "This is not the time to declare this is a welcome virus."