The overall global risk related to the new Omicron variant "is assessed as very high," according to a World Health Organisation (WHO) brief.
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Depending on how transmissible the variant is and whether it could escape immunity, "the likelihood of potential further spread of Omicron at the global level is high," the WHO brief said today (AEST).
"Depending on these characteristics, there could be future surges of COVID-19, which could have severe consequences."
The WHO expects data from ongoing further research to be available in the coming weeks.
"Further research is needed to better understand the escape potential against vaccine- and infection-induced immunity," the WHO said in the brief.
"Despite uncertainties, it is reasonable to assume that currently available vaccines offer some protection against severe disease and death."
The WHO is pushing for an international accord to help prevent and fight future pandemics amid the emergence of a worrying new Omicron COVID-19 variant.
WHO Director-General Tedros Adhanom Ghebreyesus said on Monday many uncertainties remain about just how transmissible and severe infection by the highly mutated Omicron might be.
Dr Tedros joined leaders like outgoing German Chancellor Angela Merkel and Chilean President Sebastian Pinera for a long-planned and largely virtual special session of the UN health agency's member states at the World Health Assembly.
The gathering is aimed at devising a global action plan toward preventing, preparing and responding to future pandemics.
"The emergence of the highly mutated Omicron variant underlines just how perilous and precarious our situation is," Dr Tedros said, calling for a "legally binding" agreement that wasn't mentioned in a draft text seeking consensus on the way forward. "Indeed, Omicron demonstrates just why the world needs a new accord on pandemics."
"Our current system disincentivizes countries from alerting others to threats that will inevitably land on their shores," he said, saying that South Africa and Botswana — where the new variant was detected in southern Africa — should be praised and not "penalised" for their work. That was an allusion to travel restrictions announced by many countries on air travel to and from the region.
Dr Tedros said WHO scientists and others around the world were working urgently to decipher the threat post by the new variant, saying: "We don't yet know whether Omicron is associated with more transmission, more severe disease, more risk of infections, or more risk of evading vaccines."
The world should now be "wide awake" to the threat of the coronavirus, "but Omicron's very emergence is another reminder that although many of us might think we are done with COVID-19. It's not done with us," he added.
A draft resolution set to be adopted by the World Health Assembly stops short of calling for work toward specifically establishing a "pandemic treaty" or "legally binding instrument" sought by some, which could beef up the international response when — not if — a new pandemic erupts.
European Union member countries and others had sought language calling for work toward a treaty, but the United States and a few other countries countered that the substance of any accord should be worked out first before any such document is given a name. A "treaty" would suggest a legally binding agreement that could require ratification — and would likely incur domestic political haggling in some countries.
Outgoing German Chancellor Angela Merkel, whose 16-year tenure is likely to end next week, called for "reliable financing" for WHO and increased contributions to the UN agency from its member states — while alluding to the EU position in favour of a binding agreement.
"The catastrophic impact of the COVID-19 pandemic in terms of health and the economy ought to be a lesson to us," she said by video message. "Viruses know no national borders. That's precisely why we should lay down measures to be taken to improve prevention, early detection, and response in internationally binding fashion."
Britain's ambassador in Geneva, Simon Manley, tweeted a copy of the draft text that was agreed by consensus — as required under WHO rules on such issues — and praised Chile and Australia for their work as co-chairs.
"The #Omicron variant shows yet again why we need a common understanding of how we prepare for and respond to pandemics, so we're all playing by the same rules," he wrote.
The draft makes no reference to the word "treaty" but, among other things, calls for the creation of an "intergovernmental negotiating body" among WHO member states to work out a possible deal to improve pandemic prevention, preparedness and response.
The three-day meeting that opened Monday amounts to a long-term approach: Any UN-backed agreement is likely to take many months, if not years, to be concluded and come into effect.
But it comes as many countries have been scrambling to address the emergence of Omicron that has led to travel bans across the world and sent tremors through stock markets on Friday.