LONDON - Romania has become the first European country to abolish testing and quarantine requirements for incoming foreign visitors, provided they have been vaccinated against the Covid-19 virus.
The 19 million-strong east European nation last month started conditioning free entry on the production of an official document indicating that the traveller has had both doses of an approved vaccine and that the second dose had been administered at least 10 days before arrival on Romania's soil, to ensure that peak immunity has been acquired.
The initiative positions Romania as the leader in the movement to lift travel restrictions. But the move has also revived a divisive debate in Europe about the feasibility of adopting "vaccine passports" as a way of kickstarting tourism on the continent and help local economies battered by the pandemic.
The so-called "jab and go" campaign was launched at the beginning of this year by low-cost airline carriers in Europe such as Ryanair, which are utterly dependent on a large volume of passengers and therefore have a stake in a comprehensive rather than piecemeal lifting of restrictions.
But it is also supported by the wider European travel industry, which is worried that, although vaccination campaigns are now picking up speed throughout the continent, governments still seem reluctant even to discuss lifting border closures.
An agreement to issue vaccine passports could speed up plans for the tourism industry's recovery after the pandemic; "it is an opportunity to restore a long-term perspective for customers because the organisation of a leisure trip isn't done at the last moment", argues Eric Dressin, the Secretary-General of the European Association of Travel Agents.
Some governments jumped on the bandwagon as well.
In a letter addressed to the head of the European Commission - the European Union's executive body - Mr Kyriakos Mitsotakis, the Prime Minister of Greece, whose country depends on tourism for about a fifth of its economy, demanded the introduction of vaccine passports.
The idea is not new. Some countries regularly require vaccine certificates to prove immunity against diseases such as yellow fever and several other conditions.
And behind the scenes, EU administrators have consulted the World Health Organisation about the feasibility of issuing such certificates for Covid-19 vaccines as well.
But at least for the moment, the consensus in Europe is against the adoption of such documents.
A big difficulty is reaching a consensus over the format of the vaccine "passport". Once it is adopted, it is almost guaranteed to be used by airlines as a precondition for allowing people to board flights and by immigration authorities as part of the identity checks on incoming tourists.
Therefore, the documents need to be machine-readable and tamper-proof, so that their inspection is fast, and their forgery difficult.
There are also significant obstacles to be overcome about the quantity of personal data such 'passports' should contain and, given the EU's regulations, about what will happen to the data of millions of European citizens once they leave the continent for travel outside Europe and their data is captured in computer systems operated by other governments.
Furthermore, nobody quite knows whether the vaccines currently administered are sufficient to provide long-lasting immunity.
Israel, a global leader in the speed of its vaccination efforts, is issuing those vaccinated with a printed paper document. But this cannot be used for overseas travel and has a validity of only six months.
Besides, "we do not know if a vaccinated person can still infect others", says Mr Heiko Maas, Germany's Foreign Minister, who rejects the idea of a vaccine passport.
And then, there is the fear that, if a vaccination passport is adopted as a requirement for travel, that will effectively divide Europe, with some of the poorer nations where the vaccine rollout is slower being effectively barred from travel.
"A fair balance between allowing everyone to be able to circulate is essential," argues Dr Ursula von der Leyen, the European Commission's president.
But the biggest objection to the adoption of vaccine passports comes from EU leaders such as French President Emmanuel Macron, who fears that, if these passports are introduced, it will be interpreted in France as making the vaccine compulsory, since those who will not be vaccinated will be deprived of their freedom to travel.
And, because France must contend with large numbers of people sceptical about vaccines, the last thing Mr Macron needs is to be accused of introducing compulsory vaccinations "through the back door".
As a result, most EU governments still prefer to avoid a public discussion about this topic.
Although many officials in European capitals privately admit that such a document will ultimately become an essential part in the revival of the economies of their continent.