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.

The WHO said the global surge in cases was being driven by Omicron, which is more transmissible than the previously dominant Delta variant. More than 15 million cases were reported to the WHO last week -- with millions more cases thought to have gone unrecorded.

"More transmission means more hospitalizations, 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," said Tedros.

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