LONDON — Trucks waiting to get out of Britain backed up for miles and people were left stranded at airports Monday as countries around the world imposed stringent travel restrictions on the U.K. because of a new and seemingly more contagious strain of the coronavirus in England.

A growing number of countries halted air travel from Britain, while France banned British trucks for 48 hours while the new variant is assessed.

British Health Secretary Matt Hancock said the strain is “out of control” around London and southeastern England, though experts have said it is not clear whether it is more lethal, and they expressed confidence that the vaccines now being rolled out would still be effective against it.

There were rising hopes that France would soon allow traffic to flow again, if truck drivers took coronavirus tests on arrival.

Meanwhile, t he European Union’s drug regulatory agency recommended use of Pfizer-BioNTech’s vaccine, setting the stage for the first COVID-19 shots across the 27-nation bloc. The vaccine is already being dispensed in Britain and the U.S.

The EU was expected to give final approval to the recommendation within hours. Authorities in Germany and several other European countries said they hope to begin vaccinating people on Dec. 27.

While the French ban does not prevent trucks from heading for Britain, the move stoked worries about shortages at a time of year when Britain produces very little of its food and relies heavily on produce delivered from Europe by truck. In a sign of the government’s concern, Prime Minister Boris Johnson called a meeting of the government’s emergency committee.

The ban caused chaos in Kent, the southeastern English county that is home to many of Britain’s English Channel ports. The government urged against travel to the county, but trucks snaked along the shoulders of the main highways to the ports anyway.

Around 10,000 trucks pass through Britain’s port of Dover every day, accounting for about 20% of the country’s trade in goods. British Transport Secretary Grant Shapps said France’s ban was “slightly surprising” but insisted that the public won’t notice any shortages “for the most part.”

A Croaky-Voiced French President Emmanuel Macron

France’s Minister of Transport Jean-Baptiste Djebbari indicated that a solution was coming. In a tweet, he said that “in the coming hours, at a European level, we will put a solid health protocol in place so that the flow from the United Kingdom can resume.”

And a croaky-voiced French President Emmanuel Macron, who is working from the Elysee Palace as he recovers from COVID-19, told a Cabinet meeting by video: “We are looking at systematic testing upon arrival.”

Canada, India, France, Germany, Italy, Spain and Poland were among the countries that halted flights from Britain. In the U.S., New York Gov. Andrew Cuomo said he wanted a ban on flights from Britain to New York City. Eurotunnel, the rail operator that carries passengers and freight between Britain mainland Europe, also suspended service out of the U.K.

At Germany’s Berlin and Frankfurt airports, passengers arriving from Britain had to spend Sunday night in the terminals as they awaited test results.

Sophie Taxil, a Frenchwoman who lives in London, caught a train back home from Paris and urged everyone in Britain to follow the rules.

“I live there and I need to go back there; my family is there,” she said. “I think that phlegmatic British nature suits these COVID times: Stay calm and carry on, fair play. Regarding this new strain, we don’t know. We will see.”

The moves come in the wake of Johnson’s announcement on Saturday that he was placing London and the southeast of England in a newly created tier of restrictions after scientific advisers warned that they had detected a new strain of the virus that may be more contagious.

Johnson said early indications are that the variant is 70% more transmissible and is driving the rapid spread of infections in the capital and surrounding areas.

As a result, he scrapped a planned relaxation of rules over Christmastime for millions of people and imposed other tough new restrictions in the affected zone. No indoor mixing of households will be allowed, and only essential travel will be permitted. Stores selling nonessential goods were ordered closed, putting a crimp in Christmas shopping.

The Chaos at the Border Comes at a Time of Huge Uncertainty for Britain

The European Centre for Disease Prevention and Control said that while preliminary analysis suggests the new variant is “significantly more transmissible,” there is no indication that infections are more severe. Experts, however, have stressed that even if the new strain is not more lethal, it is inevitable that more infections will lead to more hospitalizations and deaths.

The Stockholm-based agency said a few cases of the variant have been reported by Iceland, Denmark and the Netherlands. It also cited news reports of cases in Belgium and Italy.

The chaos at the border comes at a time of huge uncertainty for Britain, less than two weeks before the final stage of the country’s exit from the EU.

Though Britain left the bloc on Jan. 31, it is in a transition period during which it effectively abides by EU rules until the end of this year. Talks on a post-Brexit trade relationship were deadlocked but set to resume on Monday.

Retailers played down fears of food shortages in the short term but warned that there could be problems if the travel bans last for a while and if Britain and the EU fail to reach a trade deal.

“Retailers have stocked up on goods ahead of Christmas, which should prevent immediate problems,” said Andrew Opie, director of food and sustainability at the British Retail Consortium. “However, any prolonged closure of the French border would be a problem as the U.K. enters the final weeks before the transition ends.”

Trade association Logistics U.K. urged people to stay calm and not to rush to supermarkets to stockpile goods.

“Shoppers should not panic buy,” said Kevin Green, director of marketing and communications. “If freight gets moving again today, then the overall impact on fresh produce arriving to supermarkets should be fairly minimal.”