Traveling may soon require passengers to show a "vaccine passport" — documentation proving they have been vaccinated against COVID-19. Travel expert Rick Steves spoke with Boston Public Radio on Tuesday about the possibility of vaccination passports becoming the norm.

"We've got to be able to cross borders and prove that we are vaccinated," he said. "Whether it'll be a chip on our passport or an old-fashioned piece of paper, I don't know. But the family of nations has to figure it out."

Steves said that the idea of a COVID-19 vaccine passport isn't much different from other requirements that existed in the past.

"When I was a kid, I always traveled with the Yellow Card [or International Certificate of Vaccination]," he said. "You had to have your shots. If you didn't, at the border they wouldn't let you in. We've been able for a couple of decades to travel to developed countries without that pass. But in the future, one way or the other, we'll have that again."

Rick Steves is an author, television and radio host and the owner of the Rick Steves' Europe tour group. You can catch his television show, "Rick Steves’ Europe," weeknights at 7:30 p.m. on GBH 2 and his radio show, “Travel With Rick Steves,” Sundays at 4 p.m. on GBH.