European nations reimposed tough rules and China locked down millions Thursday, as countries scrambled to contain surging coronavirus infections driven by the Omicron variant.
Early studies from England and Scotland said infections of the Omicron strain appeared less likely to result in hospitalisation than the Delta variant.
But despite that initial data, scientists have warned that Omicron is highly contagious and could still lead to more overall severe cases.
As families across Europe prepared for Christmas, governments announced a raft of new measures to prevent intensified spread of the new strain, putting a dampener on festivities.
Spain's Catalonia was to reimpose a night-time curfew for a fortnight from Christmas Eve, while Scotland announced it would close nightclubs from next week, including on New Year's Eve.
Greece now requires people wear face masks both indoors and outside during Christmas and New Year's gatherings, as Italy contemplated imposing face masks outdoors nationwide.
Europe has been hit hard by the ongoing surge, recording 60% of global cases over the past week, according to an AFP tally from official sources on Wednesday.
Denmark said foreign visitors would be required to provide a negative COVID-19 test to enter, vaccinated or not.
13 million indoors
In even more stringent measures, China shut down a city of 13 million people on Thursday in a bid to extinguish a tiny COVID-19 outbreak and chase its zero-case goal.
China locked down the northern city of Xi'an - home to the world-famous Terracotta Warriors - to stamp out a cluster of several hundred cases.
"I think it is necessary to have the lockdown," said a Xi'an resident, who wanted to be identified only as Yuan.
Omicron has not been reported in Xi'an, with only dozens of cases of the less infectious Delta variant detected in the city of 13 million people in recent days.
But the Chinese government, in pursuit of its zero-case strategy ahead of the Beijing Winter Olympics, has ordered all Xi'an residents to stay indoors.
Only one person per household can go outside every two days to buy necessities, while non-essential businesses are closed.
February's Olympics are set to be the most restrictive mass sporting event since the pandemic began, with international spectators banned and all participants required to stay inside a closed-loop system.
All athletes must be vaccinated before landing in China, and personnel inside the bubble must undergo daily testing.
Those who test positive will not be able to participate.
COVID pills
In business, German national carrier Lufthansa said Omicron forced it to axe 33,000 flights following a drop in bookings.
Denmark discovered an illegal mink farm that had been operating despite a ban, after the country last year culled millions of the animals over fears they could carry coronavirus and jeopardise vaccine effectiveness.
But in some positive news, the US Food and Drug Administration authorised Merck's COVID pill for high-risk adults, a day after giving the green light to a similar Pfizer product.
The pill developed by Merck is taken within five days of symptom onset.
It has been shown to reduce COVID hospitalisations and deaths by 30% among at-risk people, whereas Pfizer's pill reduced the same outcomes by almost 90%.
Pills that are available at pharmacies are likely to be much easier to access than synthetic antibody treatments, which require infusions at hospitals or specialised centres.
The United States has spent $5.3 billion (€4.68 billion) procuring 10 million courses of the Pfizer treatment, according to the White House.
But health authorities maintain that vaccines are still the best protection against any variant, and are encouraging booster shots.
AstraZeneca said Thursday that a third dose of its COVID-19 vaccine "significantly" lifted antibody levels against the Omicron strain in a laboratory study.