Hoping to restore international travel, the European Union, some Asian governments and the airline industry want to create a vaccine passport.
They are working on systems for travelers to use phone apps to prove they have been vaccinated. This will help travelers avoid local quarantine requirements when they arrive.
The various efforts, however, show the lack of a central international system to check on vaccinations, either electronically or with paper documents. There are also questions about privacy and vaccine inequality.
But many countries want them. The European Union (EU) and countries like Iceland have opened their borders to vaccinated visitors. Saudi Arabia will soon start permitting its vaccinated citizens to travel to foreign countries.
Here is a look at how vaccine passports might work:
The EU, China and Japan are working on their own digital vaccination documents for international travel. Britain updated its National Health Service app last week to let travelers prove they have been fully vaccinated. It comes just as travel rules are easing.
The EU is testing a digital document to confirm COVID-19 test results or recovery from the virus. It is to start by the end of June.
It is still unclear where and how exactly travelers in the EU will have their vaccine documents checked since there are no borders. Officials in Brussels say that question will be decided by each country.
The idea is that travelers will show a QR code on their phones so it can be inspected at an airport or train station. Officials will check it against national databases.
Travelers also need a phone app to show an official vaccination document.
The EU's project includes free technology European countries can use to build their official documents.
The airline industry organization, the International Air Transport Association, has its own IATA Travel Pass. Airlines including Qantas, Japan Airlines, Emirates, British Airways and Virgin Atlantic have agreed to use the app. CommonPass is another app being used by Cathay Pacific, JetBlue, United and Lufthansa.
航空业组织国际航空运输协会拥有自己的IATA Travel Pass。包括澳洲航空、日本航空、阿联酋航空、英国航空以及维珍航空在内的航空公司已经同意使用该应用程序。国泰航空、捷蓝航空、美联航以及汉莎航空都在使用另一款名为CommonPass的应用程序。
Right now, Travel Pass and CommonPass are only available to travelers on airlines that are using them.
Both can be used with airline travel apps, so users can show they have been vaccinated when they check in online. Both also plan to be used with EU vaccine documents. CommonPass says users will be able to put in their vaccine information by mid-June.
CommonPass head Paul Meyer said vaccine passports will only become more common.
"Our expectation is it will remain a requirement for international travel," he said.
What travelers want
Business travelers seem to like the idea of vaccine passports.
Eymeric Segard is head of Geneva-based private jet company LunaJets. He believes vaccine passports will put an end to taking many COVID-19 tests while traveling. And he is not concerned with the possibility that vaccine documents might include personal information.
"I would be happy to tell anybody, yes, I am vaccinated or no I'm not vaccinated," he said.
What about false documents?
Digital vaccination documents would be hard to falsify, unlike paper documents.
IATA says it does not verify COVID-19 test results or whether travelers have been vaccinated. The organization adds that it will match travelers with their personal information of testing and vaccination sent from registered labs. There are checks to prevent identity theft.
Security and privacy
Some people fear that vaccine passports could be used to control people, restrict freedom and invade privacy.
App developers, however, say very little information is kept on phones. "This doesn't bring an additional level of privacy risk," said Kevin Trilli, because it only requires a simple "yes" or "no." He is chief product officer at Onfido which is working on vaccination document technology.
But it is still uncertain if the various vaccines passport systems will work together or whether countries will accept the documents of other nations. And what if each individual does not have a smartphone?
IATA and EU officials say they are working on that problem.
I'm Susan Shand.