While EU officials stress they will not discriminate against those who do not have a certificate, tourism-dependent countries such as Greece hope it will end the current patchwork of national rules, with agreement sought by the end of June.
* A COVID certificate would be handed out for free by health authorities in EU countries to people who received a vaccine, had a negative test or are immune, having recovered from COVID.
* No one will be obliged to use the EU certificate, the European Parliament says.
Digital green certificate
* EU lawmakers are designing the certificate along with the European Commission and EU government negotiators. Portugal, which holds the EU's rotating presidency, hopes for political agreement on the deal by the end of May to enable the certificate to be operational by June 21.
* Negotiators must decide whether faster, but less accurate, COVID-19 antigen tests can be included in the certificate.
* The European Commission proposes calling it the digital green certificate. The European Parliament suggests it should be named the EU COVID-19 certificate.
Not a vaccine passport
* It is not a vaccine passport, officials say.
* The certificate could be a paper or a digital document, with a QR code carrying encoded data that would be uploaded to the central system to allow verification in other EU countries through a single gateway.
* EU countries can link their national vaccine records to a central system using a template provided by German developers.
* EU negotiators must still agree if all vaccines can be considered for the certificate, or only those approved by the European Medicines Agency.
Linking up non-EU countries
* A dry run is due to start involving more than a dozen EU countries including France and Spain, while a full rollout of the system in all member states is planned in June.
* Linking up non-EU countries to the system is technically possible if a political agreement is sealed this month and an equivalence decision granted by the EU to share data.
Immunity to Covid-19
More than one million Europeans have received the new EU Covid health certificate being rolled out to unlock travel within the bloc.
EU Justice Commissioner Didier Reynders announced the figure to the European Parliament ahead of a vote to enshrine the document in law in time for the continent's all-important summer tourism season.
The certificate -- showing the bearer's immunity to Covid-19 either through vaccination or previous infection, or their negative test status -- is to be used for intra-EU travel from July 1, obviating the need for quarantine or further testing for travellers.
But the commission wants as many EU countries as possible to start earlier.
QR code for verification
As of Tuesday, nine EU countries were already issuing the documents -- including the sunny tourist destinations of Greece, Spain and Croatia, as well as the bloc's major source of tourists, Germany.
Bulgaria, the Czech Republic, Denmark, Lithuania and Poland were the others.
The EU Digital Covid Certificate can be presented either in online form, on a smartphone for example, or printed out on paper.
It features a QR code for verification, which border officials and venue staff can use to check against digital signatures stored securely in Luxembourg servers.
Only minimal data of the bearer are included on the certificates, to prevent identity skimming, and the EU legislation surrounding their use is due to expire after a year, so that they do not become a fixture with potential Big Brother uses in the future.
To prevent discrimination against the unvaccinated -- particularly younger Europeans who have not yet been able to access jabs given in priority to the elderly -- much emphasis has also been put on testing.
The parliament failed to make Covid tests for travel free of charge, but extracted money and concessions from the European Commission to make them more affordable.
Talks have been under way with the United States, for some sort of mutual recognition of vaccination status.
But have run up against the problem that there is no single federally backed certificated in the US, only a myriad of state and private vaccination cards almost impossible to authenticate abroad.
Now, United States considers vaccine passport
Meanwhile, the United States said Friday it is seriously considering creating a vaccine passport for Americans travelling abroad.
"We're taking a very close look at that," Homeland Security Secretary Alejandro Mayorkas said of the idea of special documentation for vaccinated Americans who want to travel overseas, as inoculation drives allow Europe and other regions of the world to start opening up from pandemic restrictions.
The administration of President Joe Biden, Mayorkas told ABC television, wants to ensure that "any passport that we provide for vaccinations is accessible to all and that no one is disenfranchised."