20 European Union countries have started issuing and accepting the Covid certificate (File).
An European Union (EU)-wide Covid certificate for easier travel comes into force on Thursday, just in time for Europe's busy summer vacation period, but the more-infectious Delta variant is already threatening to curtail its use.
The EU document -- sporting a QR code and available in digital form on smartphones or hard copy -- shows whether the bearer is vaccinated with one of the EU's approved jabs (from BioNTech/Pfizer, AstraZeneca, Moderna or Johnson & Johnson), has recovered from an infection, or has a recent negative Covid test.
Under an EU law adopted this month, the certificate does away with the need for quarantines or further testing when travelling between the EU's 27 countries or four associated European nations (Iceland, Norway, Switzerland and Liechtenstein).
Twenty EU countries have already started issuing and accepting it, with the others expected to follow suit shortly.
But a surge in the Delta variant, first detected in India and now rampant in former EU member Britain, could trigger an "emergency brake" provision suspending its acceptance.
With Delta becoming dominant in Portugal, Germany has announced a ban on incoming travellers from there except for its own citizens or residents.
Even they are required to quarantine for two weeks, regardless of vaccination or test status.
Portugal and Spain on Monday abruptly announced entry restrictions for travellers from Britain, with Lisbon requiring them to be fully vaccinated and Madrid demanding proof of vaccination or a negative Covid test.
Britain's Delta Problem
A European Commission spokesman said on Monday that Britain "is now working with us" on aligning international Covid travel requirements with the aim of having mutually accepted documents.
But Britain's rise in Delta infections -- giving it an infection rate more than four times that of the EU -- is generating deep concern on the continent.
At an EU summit last week, German Chancellor Angela Merkel criticised southern EU countries for allowing in Britons with few, if any, Covid checks.
The move gives Brits access to the entire passport-free Schengen zone and has brought them in proximity to vacationing Europeans.
Under non-binding EU guidelines, all member states were urged to allow in only fully vaccinated travellers from outside the bloc, or those with urgent reasons to visit.
But Portugal, Spain and Greece initially opted for a laissez-faire attitude, hoping to revive their vital tourist sectors.
That calculation is now changing under pressure from Germany's decisions and realisation that Delta infection rates in the EU could match current British levels within weeks.
A second European Commission spokesman said that an EU panel composed of representatives of member states and the Brussels executive was meeting on Monday to discuss "the possible application of the emergency brake".
Vaccination Hope
Evidence on whether vaccinations keep down infections, hospitalisations and deaths even from the Delta variant will be decisive for its impact on the EU Covid certificate, from scuppering the programme altogether to simply adding a note of caution to the summer rollout.
Britain, which registered its sudden rise in Delta infections in April, still has relatively low case numbers.
Some MPs in the governing Conservative party argue that vaccinations have "broken the link" between infection and deaths and the country should drop all Covid restrictions on July 19.
But many EU leaders are more cautious, hoping to slow the spread of the Delta variant to give time for more jabs.
Governments recall how surges in past variants saw lags of many weeks between spikes in infections and death rates.
AFP statistics collating official health data from across the EU show that 49.6 per cent of the bloc's population has now received at least one vaccine dose (compared with 65.3 per cent in Britain).
So far, 31.5 per cent in the EU are considered completely vaccinated.
Covid experts had initially believed "herd immunity" could be reached with 70 per cent of a population fully vaccinated, but now judge it would need 80 per cent or more immunised, given Delta's infectiousness and the fact vaccines are less effective against it.
(Except for the headline, this story has not been edited by NDTV staff and is published from a syndicated feed.)