With vaccinations on the rise and mortality rates related to COVID-19 going down in Europe and other parts of the world, many people are making plans to travel this summer and beyond. But experts say the quickly circulating Delta variant is a new concern for travelers, particularly those who are unvaccinated.

The European Union said June 18 that the United States would be added to its “safe list” of countries, a decision that should allow even unvaccinated American visitors (who can provide proof of a negative coronavirus test) to enter its 27 member states for nonessential travel. These countries, however, can impose their own restrictions and requirements for entry.

The EU decision comes the same week that the Centers for Disease Control and Prevention elevated the Delta variant of the coronavirus to a “variant of concern” as it appears to spread more quickly and may affect people more severely than earlier forms of the virus.

If you’re wondering how the variant will affect your travel plans, here is everything you need to know before booking a flight.

Where is the Delta variant spreading?

So far, the variant, first identified in India, has spread to more than 80 countries as of June 16, according to the World Health Organization. In a news conference June 10, Dr. Hans Kluge, WHO’s regional director for Europe, said the variant was “poised to take hold” in Europe.

Jennifer Nuzzo, an epidemiologist at Johns Hopkins Bloomberg School of Public Health, said this will probably be the case in other countries as well.

“If you’re out and about this summer, chances that you’re going to encounter the Delta variant, either in the U.S. or in Europe or other parts of the world, are pretty high,” she said.

The Delta variant currently makes up between 6% and 10% of U.S. cases, said Dr. Ashish Jha, dean of Brown University’s School of Public Health, adding that it will probably will be the dominant strain in the United States by August.

If you are fully vaccinated, particularly with a two-dose vaccine, “don’t worry about the Delta variant,” Jha said.

Millions of Americans have received either Pfizer-BioNTech or Moderna vaccines; both are two-dose vaccines. Studies have shown their efficacy drops only slightly when encountering variants.

“People who have been vaccinated still do quite well against this variant,” Jha said, “but it is one where you need a high degree of immunity to ward off, so you really need to have both of the doses of your vaccine.”

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