The United States on Friday authorized Moderna's Covid-19 vaccine for emergency use, paving the way for millions of doses of a second jab to be shipped across the hardest-hit country in the world.

The latest breakthrough came as many governments clamp down on socializing over Christmas and New Year, which is expected to fuel a jump in virus deaths in early 2021.

Italy on Friday announced harsh new restrictions over the holidays with many shops and all bars and restaurants closed, travel between regions banned, and only one daily outside trip per household permitted.

And parts of Sydney were heading into a fresh lockdown on Saturday, with Australian officials saying they hoped the restrictions would be enough to control a growing outbreak in time for Christmas.

With the United States now registering over 2,500 deaths a day from Covid-19, senior US officials including Vice President Mike Pence stepped up to receive early vaccinations on Friday.

Pence's public inoculation was the most high-profile attempt yet at persuading vaccine-skeptic Americans to join a national effort to halt a pandemic that has killed at least 1.66 million people and infected more than 74 million worldwide.

President-elect Joe Biden, who will take office on January 20, announced he would take the vaccine, also in public, on Monday.

- Macron 'slowed down' -

In hard-hit Europe, unease mounted after Slovakian Prime Minister Igor Matovic tested positive for Covid-19 a week after attending a European Union summit in Brussels.

The summit is believed to be where French President Emmanuel Macron caught the virus. Macron's diagnosis has led to a host of European leaders and French officials rushing into self-isolation.

The French leader acknowledged Friday he had been "slowed down" by his infection, but insisted he was still actively involved in government business including Brexit trade talks.

US President Donald Trump, who may be currently immune after recovering from Covid-19, has also signaled he would be willing to take the vaccine.

He was notably absent from Pence's vaccination event, but he has been eager to take credit for record-fast vaccine breakthroughs despite more than 310,000 American deaths from the virus.

The United States is the first nation to authorize the two-dose regimen from Moderna, now the second vaccine to be deployed in a Western country after the one developed by Pfizer and BioNTech.

Millions of doses will start shipping out as early as this weekend from cold-storage sites outside Memphis and Louisville.

Two billion doses

The European Union, facing pressure to approve vaccines, intends to begin its inoculations with the Pfizer-BioNTech dose before the end of the year, with some countries naming December 27 as a start date.

Poorer countries meanwhile received a boost Friday when the World Health Organization and partners said vaccines would be distributed early next year to the 190 countries in its Covax initiative, a pooling effort formed to ensure equitable distribution.

"The light at the end of the tunnel has grown a little bit brighter," WHO chief Tedros Adhanom Ghebreyesus told a virtual press conference.

Two billion doses have been secured from developers AstraZeneca, Johnson & Johnson, Novovax and Sanofi/GSK, though none of their candidates have so far received authorization for use.

With the vaccine rollout only just beginning however, infection rates continue to surge in many countries and a number are tightening restrictions.

In Australia a cluster of cases on Sydney's northern beaches grew to 38, with residents ordered to stay home from late Saturday other than for essential reasons.

New South Wales state Premier Gladys Berejiklian pleaded with Sydney's more than five million residents to remain in their homes.

"We're hoping that will give us sufficient time to get on top of the virus so that we can then ease up for Christmas and the New Year," she said.

In India the total number of cases moved past 10 million on Saturday, the second highest in the world, although new infection rates appear to have fallen sharply in recent weeks.

In September the vast nation looked on track to surpass the United States as the worst-hit country.

But the outbreak appears to have lost momentum in India, despite the country being home to some of the most crowded cities on the planet.

In Latin America, Mexico City's mayor announced that the capital and neighboring state would suspend almost all activities from this weekend as virus cases rise -- allowing only such essentials as the sale of food, energy, transport, manufacturing and financial services.

Brazil's President Jair Bolsonaro -- who has systemically downplayed the coronavirus -- continued to undermine the country's own immunization campaign.

He mocked the potential side-effects of the Pfizer vaccine, saying "in the Pfizer contract it's very clear: 'we're not responsible for any side effects.' If you turn into a crocodile, it's your problem."