But it is unclear when full-scale travel will again happen. A lot of things have to line up first, including vaccinations, some kind of harmonization regarding testing and government regulations.

The World Travel and Tourism Council is optimistic that a rebound is near, particularly as countries open up. Greece, for example, is set to begin opening up on May 14 and the United Kingdom on May 17.

A recent survey in the UK found people planning to spend a big portion of extra savings accumulated during the lockdowns on a personal expense or a trip. Another survey, done in Canada by Mainstreet Research for iPolitics, a Canadian news website, found that 56 percent of Canadians would travel internationally within a year of the pandemic and 81 percent would do so after a year.

The International Air Travel Association, or IATA, is piloting a travel pass that would allow travelers to manage health credentials on mobile devices. The first traveler using the pass arrived in London on a Singapore Airlines flight on March 18. The European Union is working on its own vaccine passport, hoping to have it in place before the summer and the United States is also considering COVID-19 health credentials.

The World Health Organization has established a Smart Vaccination Certificate Working Group to find ways to align all the different vaccines available around the world. The 10-country Association of Southeast Asian Nations is considering a common digital vaccine certificate.

Travel bubbles are also beginning to form. The first emerged in May 2020, with the three Baltic states of Estonia, Latvia and Lithuania.