The World Health Organization (WHO) chief says he is optimistic that the coronavirus pandemic will be defeated in 2022, provided countries work together to contain its spread.

Dr Tedros Adhanom Ghebreyesu warned against "narrow nationalism and vaccine hoarding" in a new year statement.

His comments come two years since the WHO was first notified of cases of an unknown pneumonia strain in China.

Global Covid cases now stand at 287m, while nearly 5.5m people have died.

Across the world people are marking the new year but celebrations are muted, with many countries wanting to discourage crowds gathering.

Coronavirus remains part of daily life: a disease that has shut borders, split families and in some places made it unthinkable to leave the house without carrying a mask.

Despite all this, Dr Tedros sounded a positive note in his speech, noting that there are now many more tools to treat Covid-19.

But he warned that continuing inequity in vaccine distribution was increasing the risk of the virus evolving.

"Narrow nationalism and vaccine hoarding by some countries have undermined equity and created the ideal conditions for the emergence of the Omicron variant, and the longer inequity continues, the higher the risks of the virus evolving in ways we can't prevent or predict," he said.

"If we end inequity, we end the pandemic," he added.

In other developments:

South Africa, where Omicron was first reported, has lifted an overnight curfew after announcing the country is likely to have passed the peak of new infections

A German virologist, Christian Drosten, told ZDF television he expects a "relatively normal" winter, pointing to data suggesting that Omicron cases are not as severe

Several countries, including the UK, Italy and Greece, reported record cases

Thousands more flights have been cancelled, nearly half of them in the US, as airlines struggle with crew sickness

Israel has become one of the first countries in the world to approve a fourth Covid vaccination

In his comments, Dr Tedros also alluded to low vaccination rates.

While most of the population in Europe and the Americas have received at least one dose, a WHO target of full vaccination rates in 40% of every country by the end of 2021 has been missed across most of Africa.

Dr Tedros has previously criticised wealthier nations for "gobbling up" the global vaccine supply, fully vaccinating much of their populations while others wait for their first doses.

The WHO has set a new goal for 2022: vaccinate 70% of people in all countries by July to end the pandemic.