(Bloomberg) -- The world’s biggest online travel agency is in favor of vaccine passports that would make it safer and easier for people to travel.

“We need a way that tourists can go to a country but prove that they are safe to travel so that governments are willing to let people come,” said Booking Holdings Inc. Chief Executive Officer Glenn Fogel in an interview on Bloomberg Television Thursday.

Fogel added that taking a test three days prior to traveling is “not the greatest system” and a “technological solution” is needed. “We want to do something that is easier so we can bring back international travel.”

Booking Holdings -- which owns brands including Priceline, Kayak, Agoda and OpenTable -- has seen an increase in demand but is still “significantly below” 2019 levels.

While the outlook for summer travel looks bright, Fogel said fast-spreading variants pose a risk to a rebound. “It is a race between the virus and the vaccines.”

Norwalk, Connecticut-based Booking’s revenue primarily comes from international markets, especially Europe. Fogel said that an improvement in the travel industry will also hinge on vaccine distribution outside of wealthy countries. “The world is only as safe as everyone is vaccinated, and we need better-developed countries to provide the assistance.”

Booking shares were little changed Thursday morning in New York at $2,420.50. The stock has gained 8.5% so far this year.

©2021 Bloomberg L.P.