COVID-19: What you need to know about the coronavirus pandemic on 20 December

Confirmed cases of COVID-19 have passed 274.7 million globally, according to Johns Hopkins University. The number of confirmed deaths has now passed 5.35 million. More than 8.7 billion vaccination doses have been administered globally, according to Our World in Data.

Children aged 5-11 in Portugal have begun receiving COVID-19 vaccines, after the country's health authority approved the Pfizer/BioNTech jab.

US officials have urged Americans to get booster shots, wear masks and be cautious if travelling over the holiday period, to reduce transmission of the fast-spreading Omicron COVID-19 variant.

Thailand has reported its first local transmission of the Omicron COVID-19 variant, a health ministry official announced.

A COVID-19 booster shot produced by China's Sinopharm had 'significantly lower' neutralising activity against the Omicron variant, Chinese researchers said in a paper. But, the authors cautioned that the results were not equal to how well a Sinopharm booster could shield recipients from Omicron, as neutralization is only part of the human immune response.

The UK government is monitoring COVID-19 data on an almost hourly basis, Health Secretary Sajid Javid said on Sunday, and will 'do what is necessary' to tackle the spread.

Iran has reported its first confirmed case of the Omicron COVID-19 variant.

The Omicron COVID-19 variant has now been reported in 89 countries, the World Health Organization said on Saturday - a figure which is likely to have risen since. And, in those areas with community transmission, the number of cases is doubling every 1.5 to 3 days, the organization said.

The Omicron variant is spreading rapidly in countries with high levels of population immunity, but it is unclear if this is due to the virus's ability to evade immunity, its inherent increased transmissibility, or a combination of both, the WHO said.

"There are still limited data on the clinical severity of Omicron," the WHO said. "More data are needed to understand the severity profile and how severity is impacted by vaccination and pre-existing immunity."

"There are still limited available data, and no peer-reviewed evidence, on vaccine efficacy or effectiveness to date for Omicron."

A snap COVID-19 lockdown began yesterday in The Netherlands after the Dutch government announced a series of measures on Saturday aimed at slowing the expected surge in COVID-19 cases caused by the fast-spreading Omicron variant.

Prime Minister Mark Rutte announced the shutdown on Saturday evening, ordering the closure of all but essential stores, as well as restaurants, hairdressers, gyms, museums and other public places from Sunday until at least 14 January.

Other measures include a recommendation that households receive no more than two visitors and that gatherings outside are also limited to a maximum of two people.

"The Netherlands is again shutting down. That is unavoidable because of the fifth wave that is coming at us with the Omicron variant," Rutte told a televised news conference.