The more infectious Omicron variant of COVID-19 appears to produce less severe disease than the globally dominant Delta strain but should not be categorised as "mild," World Health Organisation officials say.
Janet Diaz, WHO lead on clinical management, said early studies showed there was a reduced risk of hospitalisation from the variant first identified in southern Africa and Hong Kong in November compared with Delta.
There appears also to be a reduced risk of severity in both younger and older people, she told a media briefing from WHO headquarters in Geneva.
The remarks on the reduced risks of severe disease chime with other data, including studies from South Africa and England, although she did not give further details about the studies or ages of the cases analysed.
The impact on the elderly is one of the big unanswered questions about the new variant as most of the cases studied so far have been in younger people.
"While Omicron does appear to be less severe compared to Delta, especially in those vaccinated, it does not mean it should be categorised as mild," director general Tedros Adhanom Ghebreyesus said at the same briefing in Geneva.
"Just like previous variants, Omicron is hospitalising people and it is killing people."
He warned of a "tsunami" of cases as global infections soar to records fuelled by both Omicron and Delta, healthcare systems are overwhelmed and governments struggle to tame the virus which has killed more than 5.8 million people.
Tedros repeated his call for greater equity globally in the distribution of and access to vaccines.
Based on the current rate of vaccine rollout, 109 countries will miss the WHO's target for 70 per cent of the world's population to be fully vaccinated by July, Tedros added.
That aim is seen as helping end the acute phase of the pandemic.
WHO adviser Bruce Aylward said 36 countries had not even reached 10 per cent vaccination cover.
Among severe patients worldwide, 80 per cent were unvaccinated, he added.
In its weekly epidemiological report on Thursday, the WHO said cases increased by 71 per cent, or 9.5 million, in the week to January 2 from a week earlier while deaths fell by 10 per cent or 41,000.
Case counts doubled in North and South America and registered a 65-per-cent rise in Europe.
Maria van Kerkhove, the WHO's technical lead on COVID-19, said individuals still had the power to influence the course of the pandemic and keep case counts down.
People needed to follow simple steps like keeping distance from people who do not belong to their household, wearing face masks properly and making sure any rooms they use are well ventilated.
She urged people to avoid crowded places and counselled schools, businesses and government agencies to invest in good ventilation systems.
"Don't give up, we will get out of this pandemic together," she said.
Another variant B.1.640 - first documented in multiple countries in September 2021 - is among those being monitored by the WHO but is not circulating widely, van Kerkhove said.
There are two other categories of greater significance the WHO uses to track variants - "variant of concern," which includes Delta and Omicron, and "variant of interest".
with reporting from DPA