The United States has reported its first case of community transmission of Omicron and President Joe Biden prepared to lay out his strategy to fight the coronavirus over the northern hemisphere winter as the variant spread across the globe.
As the world scrambled to contain the spread of Omicron, health authorities in the northern US state of Minnesota said the infected resident was a fully vaccinated adult male who had recently travelled to New York City.
The person told state health investigators he attended the Anime NYC 2021 convention at the Javits Center from November 19 to 21 and developed mild symptoms on November 22.
"We are aware of a case of the Omicron variant identified in Minnesota that is associated with travel to a conference in New York City and we should assume there is community spread of the variant in our city," New York City Mayor Bill de Blasio said.
"We are working closely with the State and the CDC, as well as the Javits Center's event organisers, and our Test and Trace Corps will be contacting conference attendees," he said in a statement.
Germany announced it would bar the unvaccinated from all but essential businesses such as grocery stores and pharmacies while legislation to make vaccination mandatory will be drafted for early next year.
"We have understood that the situation is very serious," Chancellor Angela Merkel told a news conference.
A vaccination mandate could take effect from February 2022 after it is debated in the Bundestag and after guidance from Germany's Ethics Council, she said.
Eager to avoid derailing a fragile recovery of Europe's biggest economy, Germany kept businesses open to the almost 69 per cent of the population that is fully vaccinated as well as those with proof of having recovered from the virus.
UK Prime Minister Boris Johnson received his COVID-19 booster shot on Thursday and urged others to follow suit to help the country fend off the Omicron variant of coronavirus.
But WHO emergencies director Mike Ryan was on Wednesday critical of developed countries pushing booster shots for large parts of their fully vaccinated populations when even vulnerable people in many poorer regions had had no vaccination at all.
"There is no evidence that I'm aware of that will suggest that boosting the entire population is going to necessarily provide any greater protection for otherwise healthy individuals against hospitalisation or death," he said.
In the United States, Biden was due to speak at the National Institutes of Health (NIH) later on Thursday to announce steps including extending requirements for travellers to wear masks through mid-March.
By early next week the US will require inbound international travellers to be tested for COVID-19 within a day of departure regardless of vaccination status.
And private health insurance companies will be required to reimburse customers for at-home COVID-19 tests as part of a winter strategy that Biden is due to announce.
"The president is going to unveil a very robust plan, pull out all the stops to prepare for the winter and to prepare for the new variant," White House COVID-19 response coordinator Jeff Zients told broadcaster MSNBC.
Much remains unknown about Omicron, which was first detected in southern Africa last month and has been spotted in at least two dozen countries just as parts of Europe were already grappling with a wave of infections of the Delta variant.
South Africa said it was registering an increase in COVID-19 reinfections in patients contracting Omicron - with people who have already had the illness getting infected again - in a way that it did not see with other variants.
In the Netherlands, health authorities called for pre-flight COVID-19 tests for all travel from outside the European Union after it turned out that most of the passengers who tested positive after arriving on two flights from South Africa on November 26 had been vaccinated.
The first known US case, announced on Wednesday, was a fully vaccinated person in California who had travelled to South Africa.
Two French cases, in the greater Paris region and in eastern France, were passengers arriving respectively from Nigeria and South Africa.
Iceland officials said the first Omicron case in the country had been reported in a man who had not travelled overseas.
Russia has imposed a two-week quarantine for travellers from some African countries including South Africa, the Interfax news agency said, quoting a senior official.
In France, the country's top scientific adviser, Jean-Francois Delfraissy, said the "true enemy" for now was still the more familiar Delta variant of the virus, spreading in a fifth wave.
Australian Associated Press