A "tsunami" of omicron and delta Covid-19 cases will pile pressure on health systems already being stretched to their limits, the World Health Organization (WHO) warned on Wednesday.

The WHO said the delta and omicron variants of concern were "twin threats" that were driving new case numbers to record highs, leading to spikes in hospitalisations and deaths.

The WHO said new global cases had risen by 11 per cent last week, while the United States and France both registered record daily case numbers on Wednesday.

"I am highly concerned that Omicron, being more transmissible, circulating at the same time as Delta, is leading to a tsunami of cases," WHO chief Tedros Adhanom Ghebreyesus told a press conference.

"This is and will continue to put immense pressure on exhausted health workers, and health systems on the brink of collapse."

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.

'Moral shame'

The WHO reflected on the fight against Covid-19 in 2021 and hoped that next year would see an end to the acute stage of the pandemic — but warned that it would rest on greater vaccine equity.

The WHO wanted 40 percent of the population in every country fully vaccinated by the end of the year and has a target of 70 percent coverage by the middle of 2022.

Tedros announced that 92 of the WHO's 194 member states were going to miss the 40 per cent target.

"This is due to a combination of limited supply going to low-income countries for most of the year and then subsequent vaccines arriving close to expiry and without key parts like the syringes," he said.

"It's not only a moral shame, it cost lives and provided the virus with opportunities to circulate unchecked and mutate. In the year ahead, I call for leaders of government and industry to walk the talk on vaccine equity.

"While 2021 has been hard, I ask everyone to make a New Year's resolution to get behind the campaign to vaccinate 70 per cent by the middle of 2022."

Misinformation and populism

Tedros slammed the attitude of richer countries accusing them of hogging the weapons to combat Covid-19 — and leaving the back door open for the virus.

"Populism, narrow nationalism and hoarding of health tools, including masks, therapeutics, diagnostics and vaccines, by a small number of countries, undermined equity, and created the ideal conditions for the emergence of new variants," he said.

Meanwhile disinformation had been a constant distraction in 2021, hampering efforts to beat the pandemic.

"In the huge waves of cases currently seen in Europe and in many countries around the world, misinformation which has driven vaccine hesitancy is now translating to the unvaccinated disproportionally dying," he said.

Tedros lamented that while there were 1.8 million recorded deaths in 2020, there were 3.5 million in 2021 — and the true number would be much higher.