I've thought long and hard about doing this. At the end of the day, the main reason I haven't is that I wouldn't be able to get much time off work/school and definitely couldn't stick around long enough to get both shots. But it's rough out here, y'all.

In Berlin, Lucas Mathis booked a flight next month to see his parents in Oklahoma City. He plans to get fully vaccinated while he’s there. Germany, which has given at least one dose to 18% of its population, shows no signs of easing lockdown measures. His daily routine of isolation and meandering walks was driving him bananas.

“The idea of going out to eat on a restaurant’s patio and having tacos with my parents sounds like a trip to Disneyland at this point,” said the 33-year-old computer programmer. “I feel like I might cry when it happens.”

Getting vaccinated in Oklahoma would ease his mind upon returning to Germany, he said, knowing he was less likely to get ill or spread disease when grocery shopping. His friends support his decision, as does his Canadian wife, whose home country has a 22% vaccination rate.

Mr. Mathis is still uneasy. “It’s going to be kind of weird to be the only person in my friend group here with a vaccine once I return,” he said.