The European Union on Friday backtracked on a threat to restrict exports of coronavirus shots to Northern Ireland in its growing row with Britain, as the WHO warned against "vaccine nationalism".

Outbreaks are raging around the globe with COVID-19 deaths nearing 2.2 million, and while wealthy countries fight over limited vaccine supplies, there are fears the less privileged will not get access for a long time.

British-Swedish firm AstraZeneca has said it can only deliver a fraction of its vaccine doses promised to the EU and Britain because of production problems, but both sides are demanding their pledges are met.

The EU threatened to restrict vaccine exports to Northern Ireland by overriding part of the Brexit deal with Britain that allowed the free flow of goods over the Irish border, but backed down after British Prime Minister Boris Johnson voiced "grave concerns".

The European Commission will "ensure that the Ireland/Northern Ireland Protocol is unaffected", the EU commissioner said in a statement late Friday.

That came after the EU released a redacted version of its contract with AstraZeneca, while announcing a mechanism that could allow it to deny the export of vaccines made on European soil.

The AstraZeneca vaccine on Friday became the third to get EU approval after Pfizer/BioNTech and Moderna, but it came under the shadow of the bitter diplomatic row.

"I expect the company [AstraZeneca] to deliver the 400 million doses as agreed," tweeted European Commission chief Ursula von der Leyen, as she announced the authorisation.

The supply issue is a huge blow to Europe's already stumbling vaccine rollout.

 'Vaccine nationalism' 

The EU-Britain tussle has highlighted the impact of shortages on ambitious mass vaccination programmes, even on wealthy nations, and fears are growing that the developed world is hogging doses, leaving poorer nations behind.

World Health Organisation chief Tedros Adhanom Ghebreyesus warned Friday against "vaccine nationalism”, saying there was a "real danger that the very tools that could help to end the pandemic — vaccines — may exacerbate” global inequality.

Parts of Africa and Asia have only just started securing and rolling out vaccinations.

The global scramble for shots comes as more troubling data emerges on new variants of the coronavirus, which is known to have infected more than 101 million people worldwide.

Variants first detected in Britain, Brazil and South Africa are believed to be more contagious.

Scientists are concerned that the South African variant may elude some vaccines, a potential stumbling block in the global effort to defeat COVID-19 through mass inoculation.

New data on Thursday and Friday showed average effectiveness of 89 and 66 per cent for shots from Novavax and Johnson & Johnson.

But while Novavax’s jab was highly effective against the British variant, both were less effective against the South African strain.

Pfizer and Moderna have said their vaccines are effective against the variants.

WHO experts continued their closely watched scientific mission Saturday in Wuhan, China, where the coronavirus first emerged in late 2019, hoping to uncover more clues about the origins of the pandemic.

They visited Jinyintan hospital, which received the first patients officially diagnosed with COVID-19.

Australian Open boost 

With vaccine rollouts still in their early stages, movement restrictions remain among the few options for governments to try to stop the spread of COVID-19.

Surges have overwhelmed healthcare systems even in rich countries such as Britain and the United States, while Mozambique President Filipe Nyusi warned that hospitals across southern Africa were "rapidly reaching the limit of their capacities”.

Citing concerns over the new strains, Germany on Friday said it would ban travel from countries where the variants are prevalent, starting this weekend, while Canada announced hotel quarantine for all new arrivals.

France has announced the closure of its borders to all non-EU travellers except for essential travel.

The pandemic has shredded the international sports calendar, with doubts growing about the already delayed Tokyo Olympics.

But there was good news out of Australia, which has largely kept its outbreak under control with aggressive travel restrictions.

Australian Open organisers said Saturday that between 25,000 and 30,000 tennis fans will be allowed to watch the season’s opening Grand Slam.