These digital credential systems can show whether someone has been vaccinated against COVID-19 and can help businesses limit access to those who have been inoculated. The systems were designed to increase health and safety at various venues, but experts warn of pushback over concerns on privacy and personal choice.

"What we're seeing throughout the pandemic is people guarding their personal rights, and I think a lot of people will find that intrusive in their day to day," said Jonathan Day, an associate professor of hospitality and tourism management at Purdue University.

The push for a standardized credential system comes as various venues plan to open only to vaccinated guests. Some cruise lines are limiting service to vaccinated travelers, and sports teams including the Miami Heat plan to offer sections only to vaccinated fans.

A handful of passports are already in the works, including two in Las Vegas. It is not yet clear if any Las Vegas businesses will limit access solely to vaccinated guests.