The simultaneous spread of the Delta and Omicron variants of the coronavirus is creating a "tsunami of cases" that continue to put immense pressure on health systems that are already on the brink of collapse, the WHO warned on Wednesday.

"Delta and Omicrom are now twin threats driving up cases to record numbers, leading to spikes in hospitalisation and deaths," WHO chief Tedros Adhanom Ghebreyesus told a press conference.

He said the pressure on health systems was not only due to new coronavirus patients, but also large numbers of health workers falling ill with Covid.

The WHO said over 6.5 million cases new cases had been recorded worldwide in the week between Dec 22-28, while the United States and France both registered a record number of daily infections on Wednesday.

Tedros said countries must share vaccines more equitably and warned that the emphasis on boosters in richer countries could leave poorer nations short of doses.

He said the WHO was campaigning for every country to hit a target of 70% vaccine coverage by the middle of 2022, which would help end the acute phase of the pandemic.

More than 281 million people have been reported to be infected by the novel coronavirus globally and more than 5 million have died since the outbreak of the pandemic, according to a Reuters tally.

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