(CNN) — The United States has reopened its borders to vaccinated international travelers, ending a 20-month travel ban at the same moment Europe is battling a surge of COVID-19 cases that has pushed the continent back into the epicenter of the pandemic.

Fully vaccinated travelers from 33 countries — including the United Kingdom and much of Europe — can now enter the US without needing to quarantine, provided they have proof of vaccination and a negative viral test.

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Families and friends separated since the start of the pandemic streamed into airports across major European cities on Monday morning, excited to see loved ones for the first time since former President Donald Trump imposed tough travel restrictions at the outset of the pandemic in an effort to control the virus.

But beyond these happy scenes is a darker backdrop.

Europe is in the grip of a fresh wave of coronavirus cases, with the World Health Organization last week warning the region is once again “at the epicenter” of the pandemic.

Large swathes of Europe are battling to beat back surges of the Delta variant, amid the relaxation of restrictions and stuttering vaccine rollouts in some countries, with the WHO warning half a million Europeans could die with COVID-19 in a potentially devastating winter.

Germany on Monday recorded its highest seven-day incidence rate since the pandemic began. The same day, neighboring Austria banned unvaccinated people from restaurants and hotels amid a surge in cases. Iceland has also reintroduced masks and social-distancing rules following a rise. And cases are hovering at record levels in Russia, Ukraine and Greece.

From Paris to the US, with love

France too has seen a sharp rise in cases in the last month, with President Emmanuel Macron set to address the nation on Tuesday — his first major TV speech since July when he announced controversial mandatory vaccinations for all health workers.

Nonetheless, a steady stream of masked travelers arrived at Paris’ bustling Charles de Gaulle airport on Monday morning, excited to finally see loved ones in the US.

The airport’s departures board was filled almost back-to-back with flights to destinations in the US. Some travelers wondered if this was a window of opportunity to see loved ones before another COVID-19 wave in Europe shut them off from the world again.

One traveler, Maxime Barei, told CNN he was on his way to visit his two children in Los Angeles where they are studying. It’s the first time he’s been able to go to the US in two years. “We can call it freedom,” Barei said, adding “I hope it continues.” Amid the uncertainty over another wave in Europe, he said: “I don’t know if the borders will be closed again another time.”

Another woman, Maria Giribet Caldentey, was also headed to California to see her twin grandchildren, after already postponing the trip once before due to border closures. “I’m leaving the first day they will allow me to leave … I’ve got butterflies,” she said. It’s the first time Caldentey has traveled alone, after her husband died last year, and she admitting to having a few nerves around the trip. But mostly she was relieved to finally be going on a journey she’s been “dreaming of since July.”

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Many European airlines — including Lufthansa, Virgin Atlantic, Swiss Air and British Airways — reported full or nearly full flights on the first day the US reopened to vaccinated international travelers.

British Airways and Virgin Atlantic celebrated the easing of restrictions with a dual take-off of their first flights from Heathrow airport in London to JFK airport in New York. Air France said it would increase its capacity after the US announcement led to a significant increase in bookings, particularly on routes to New York, Miami and Los Angeles over the Christmas holiday period.

“After an unprecedented 18 month closure, today we celebrate the reopening of the US to the nearly 76% of the adult EU population who have since been vaccinated against COVID-19. Europe’s airlines look forward to reuniting families and friends who have been separated for far too long,” Europe’s largest airline association, Airlines 4 Europe, said in a statement:

‘Good for the economy, good for the people’

Meanwhile in some parts of Europe, experts have expressed concern that further rises in infections, coupled with seasonal winter colds, could place health care workers under unmanageable pressure through Christmas and in the New Year.

On Monday, Germany’s daily COVID-19 infection rate climbed to 201.1 cases per 100,000 people, its highest since the start of the pandemic, according to the country’s Robert Koch Institute of infectious diseases (RKI). In some eastern states, like Saxony and Thuringia, the incident rate was more than double that at over 400.

However there was little mention of rising cases from German politicians who welcomed the US travel reopenings Monday, with the Minister of Economics and Technology, Peter Altmaier, welcoming the move in a statement, saying it was “good for our transatlantic relations, good for the economy and good for people.”

So far, almost 80% of the adult German population has been fully vaccinated, a slightly lower figure than other major EU countries like France, Spain and Italy, according to the European Center for Disease Control (ECDC). But the rollout has been extremely unequal across the bloc; on the other side, Romania and Bulgaria have fully vaccinated only 40% and 27% of their adults, respectively.

Elsewhere, the UK has been enduring a stubborn streak of new infections since the end of the summer, but has resisted implementing measures like mask mandates or vaccine passes which have become commonplace across Europe.

The US has suffered its own devastating COVID-19 toll, recording more than 46 million cases and over 754,400 deaths, the highest worldwide, according to the John Hopkins University. More recently, COVID-19 deaths and hospitalizations have been dropping nationally, though there have been regional spikes.

Earlier this month the world passed the grim milestone of 5 million COVID-19 deaths since the beginning of the pandemic — a mark the UN Secretary-General Antonio Guterres called “a painful new threshold.”

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