The E.U. May Reopen to Vaccinated American Tourists. Here’s What to Know.

BRUSSELS — A yearlong ban on all but the most essential travel from the United States to the European Union may be lifted soon, just in time for summer vacation.

In an interview with The New York Times on Sunday, Ursula von der Leyen, president of the European Commission, said she would put forward a policy proposal for the union’s 27 member states to accept visitors who have received E.U.-approved vaccines, paving the way for a reopening of travel.

“The Americans, as far as I can see, use European Medicines Agency-approved vaccines,” Ms. von der Leyen said. “This will enable free movement and the travel to the European Union.”

But many questions remain. Here is what to know.

While Ms. von der Leyen’s comments signaled a major shift from the current policy, the details of exactly how and when the restart of travel would begin are still being worked out.

In her initial comments, Ms. von der Leyen did not offer a timeline or offer details on how tourism would be enabled. But her public comments suggest that the European Commission will officially recommend the change in travel policy soon.

When asked about the shift during a Monday briefing, Eric Mamer, the commission’s spokesman, said that there were still unanswered questions.

“It is clear this is a policy direction. Many factual questions will need to be answered, but it’s important to set the horizon toward an objective,” he said.

Countries like Spain, Italy, Portugal and Croatia, where tourism is the lifeblood of the economy and millions of American tourists normally visit each summer, are likely to jump at the opportunity to reopen.

Greece has already made such a move, declaring last week it would begin welcoming tourists from the United States with a negative Covid-19 test or a vaccination certificate, starting Monday.

Individual member states may also reserve the right to keep stricter limits in place. Some might not permit citizens from outside the bloc to visit at all or could choose to enforce restrictions like quarantines.

When Brussels might change the policy guidelines for the bloc as a whole remains unclear and will depend not only on the pace of vaccinations in Europe and America but the broader pandemic situation.

Ms. von der Leyen’s comments made it clear that the eligibility of visitors from the United States would be linked to the use of approved vaccines and the virus situation in the country, so the assumption is that some form of a so-called “vaccine passport” could be used.

The practicality of issuing vaccine certificates that are broadly readable in each nation in the bloc, and launching the technology to do that, could pose a challenge.

U.S. and E.U. officials have already spent weeks in discussions on how exactly the program would work, both technically and logistically, and those discussions are continuing, officials in Brussels said.

But in the interim, it is possible that a low-tech solution could be used before a broader program is launched to enable people to travel freely on the basis of vaccination. For example, an adult traveler to Europe could get an equivalent to an E.U. vaccine certificate on arrival, after showing a bona fide certificate issued by his or her own government.

The hope, officials said, is that this step would soon be unnecessary as vaccine certificates issued by foreign governments would be acceptable and readable in the European Union, and vice versa.

Questions have already begun about whether children traveling to the bloc would need to be vaccinated. Children in the United States and Europe are not currently being vaccinated for the coronavirus.

Since E.U. authorities would likely try to write any travel policy in a way that was reciprocal, it seems unlikely children traveling into Europe would have to provide proof of vaccination.

So far, the bloc’s leaders have only weighed in publicly on the conditions for travelers from the United States, and have not mentioned any other countries that could benefit from such a reopening.

The European Commission, responding to questions about the interview Monday during a news briefing, did say that a mutual agreement on how to recognize vaccine certificates, the use of vaccines approved by the European Medicines Agency and a positive virus situation in both the European Union and the country of interest would be required to take that step.

It also said that it was not yet engaged in discussions with the British authorities about a similar arrangement.

No. While the European Union has already taken tentative steps toward rolling out a “Digital Green Certificate” to enable safe travel within the bloc for European residents, the use of such a system is still months away.

The European Commission issued recommendations on the measures last month, in an attempt to standardize the documentation needed by travelers within the E.U. So far, travelers have been asked to provide various documents including medical certificates, test results, and declarations ahead of travel, making it hard to move around within the bloc.

The proposed certificate would provide digital proof that a person has been vaccinated against the coronavirus, has received a negative test result, or has recovered from the virus.

The initiative came after a push by tourism-dependent members of the European Union to salvage the summer travel season.

Matina Stevis-Gridneff reported from Brussels and Megan Specia from London.