The WHO on Friday called for a worldwide acceleration in vaccine roll-outs – as well as a ramp-up in efforts to study the sequencing of the virus, to tackle troubling new strains emerging around the world.

“I want to see vaccination under way in every country in the next 100 days so that health workers and those at high risk are protected first,” Tedros Adhanom Ghebreyesus told a press conference in Geneva.

His call came as infections snowballed, with 724,000 new cases recorded on average per day globally over the past week, according to AFP’s tally – a record 10 per cent increase on a week earlier.

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SCMP Explains: What's the difference between the major Covid-19 vaccines?

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While countries from Spain to Lebanon have announced record caseloads, the surge has been most marked in Latin America and the Caribbean, where confirmed cases leapt 26 per cent this week.

“You have my word: we will manage the hell out of this operation,” said Biden, five days before he assumes leadership of the world’s hardest-hit country, where the death toll is approaching 400,000.

Health and Human Services Secretary Alex Azar said the US does not have a reserve stockpile of Covid-19 vaccines, but it is confident that there will enough produced to provide a second dose for people.

“We now have enough confidence that our ongoing production will be quality and available to provide the second dose for people. So we’re not sitting on a reserve anymore. We’ve made that available to the states to order,” Azar told NBC News.

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In Europe, which has suffered more than 650,000 coronavirus deaths, there are concerns that delays to the Pfizer jabs could further slow a vaccine roll-out that has already faced heavy criticism.

Pfizer, which jointly developed its vaccine with German company BioNTech, said EU countries could expect delayed deliveries in the coming weeks due to work being done at its plant in Belgium.

It promised that there would be “a significant increase” in shipments in March, and the European Commission said all vaccines ordered by the bloc for the first quarter would be delivered on time.

But ministers from Denmark, Estonia, Finland, Latvia, Lithuania and Sweden said in a joint letter that the situation was “unacceptable” and “decreases the credibility of the vaccination process”.

Many countries have meanwhile doubled down on restrictions as Covid-19 cases mount.

Portugal entered a fresh lockdown on Friday, and new curbs on populations were announced from Italy to Brazil.

Brazil’s northern Amazonas state announced a curfew from 7pm to 6am, with the health system in state capital Manaus at breaking point.

The city’s hospital intensive care units have been at 100 per cent capacity for the past two weeks, while medical workers are battling a shortage of oxygen and other essential equipment.

Fear has been growing that a new strain of the virus found in Brazil could be more contagious, just like the variants recently found in Britain and South Africa.

Britain has banned all arrivals from South America and Portugal in a bid to prevent the new variant arriving, while also announcing on Friday that all people arriving in the UK must show negative test results and quarantine.

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Warnings from cash-strapped companies and governments about the economic fallout of the crisis are also piling up.

Italy said it was seeking to borrow an extra 32 billion euros, while senior French rail executive Christophe Fanichet said Eurostar was in “a very critical” state as the pandemic has reduced its service to just one London-Paris connection per day.

The UN aviation agency on Friday predicted “prolonged depressed demand” for air travel and more financial woes for airlines, following a year of fewer flights and big losses blamed on the pandemic.

Air travel plunged 60 per cent in 2020 as nations closed borders and restricted travel to slow the spread of Covid-19, the International Civil Aviation Organization said in a report.

The pandemic has also slowed global migration by nearly 30 per cent, with around two million fewer migrants between 2019 and 2020, according to a UN report released on Friday.