That’s the route that Dr. Amber Schmidtke, 40, and her family, who live in Kansas City, took during the pandemic. Over the summer, for example, she and her family packed up their camper and traveled for three weeks through Colorado and Utah. Camping, she said, is “sort of pandemic-proof.”

In March, after she and her husband got vaccinated, they booked a Labor Day trip to Hawaii with their children, 10 and 12, with another family of mixed vaccination status.

“We fully expected that there would be a pediatric vaccine by now,” Dr. Schmidtke said. But a few weeks ago, as she saw cases rise in Hawaii and reflected on how the virus has disproportionately harmed people of color, including Native Hawaiians, she decided to cancel her trip.

Dr. Schmidtke is particularly attuned to the spread of the Delta variant because of her work as a Covid researcher at the University of St. Mary in Kansas.

“I may be a little more paranoid than some parents,” she said, but “especially with unvaccinated kids, it’s just a risk that we weren’t willing to take.” She added that she didn’t want to “be responsible for any sort of outbreak” in Hawaii.

Bookings have already started to pick up for next year. Gemma Jamieson, a spokeswoman for Skyscanner, a flight-booking app, said in an email that bookings for 2022 created in the last week were up 30 percent compared to the same time in July. The top bookings were to Cancún, London, Paris, Rome and Tokyo, indicating a continued demand for travel worldwide.

It’s too early to tell how these bookings will be affected by the European Union’s action this week. But, said Dia Adams, a travel expert at Forbes Advisor, “I do think the top line will scare some European travelers off booking their trips.”