The EU's drug regulator on Monday approved a fifth COVID jab as the US warned of a bleak winter with the Omicron variant spurring new waves of infections globally.
Since it was first reported in South Africa in November, Omicron has been identified in dozens of countries, dashing hopes that the worst of the pandemic is over.
Despite indications it is not more severe than the Delta variant - still the dominant strain - Omicron has been shown in early data to have higher transmissibility and a worrying resistance to vaccines.
On Monday, the European Medicines Agency's human medicines committee approved Novavax, which uses a more conventional technology that the biotech firm hopes will reduce vaccine hesitancy.
"EMA has recommended granting a conditional marketing authorisation for Novavax's COVID-19 vaccine Nuvaxovid to prevent COVID-19 in people from 18 years of age," it said after an extraordinary meeting at its Amsterdam headquarters.
It is the fifth vaccine approved in the bloc after shots from Pfizer, Moderna, AstraZeneca and Johnson & Johnson, and the EU has already signed a deal to buy up to 200 million doses of the two-shot Novavax vaccine.
The firm says its vaccine showed 90.4 per cent efficacy against COVID-19 in a North American trial.
Governments are scrambling to roll out booster shots to populations, with early data suggesting that a third dose offers increased protection against Omicron.
Moderna said on Monday that a full dose of its vaccine given as a booster provides more antibody protection against the variant than currently authorised half-strength injections.
CEO Stephane Bancel called the results "reassuring", adding that the company is continuing to develop an Omicron-specific jab.
WEF off
As the pandemic gathers pace again, familiar restrictions are once again being rolled out as fears loom large.
The World Economic Forum said it was postponing its annual summit of the world's rich and powerful in the Swiss ski resort of Davos scheduled for January 17 to 21 due to the new variant.
"Despite the meeting's stringent health protocols, the transmissibility of Omicron and its impact on travel and mobility have made deferral necessary," the WEF said Monday.
And in the US, top pandemic adviser Anthony Fauci meanwhile warned of tough times ahead with stretched hospitals and over-optimism about the apparant reduced severity of Omicron.
"One thing that's very clear... is (Omicron's) extraordinary capability of spreading," Fauci told NBC News. "It is just... raging through the world."
"Our hospitals, if things look like they're looking now in the next week or two, are going to be very stressed," particularly in areas of the country with low levels of vaccination, Fauci said.
While a little more than 70 per cent of the US population has had at least one shot, another 50 million eligible people remain unprotected, Fauci said.
"With Omicron... it is going to be a tough few weeks to months as we get deeper into the winter," he added.