Digital vaccine certificates will be ready in June at the latest, Spanish Foreign Minister Arancha González Laya has said.
European Union leaders agreed earlier this year to work on the certificates to try to kickstart the tourism industry.
Speaking on Wednesday, Ms Laya said the scheme would be a good tool for European citizens and "if all goes well, we will have a vaccination certificate in June at the latest".
"If it can be in mid-May, better but not later than June," she added.
The certificates would not prevent those without the jab from travelling, she said, but people who had one would be able to pass through EU borders faster.
Ms Gonzalez Laya told Spain's Onda Cero radio on Wednesday that the European Parliament had agreed to fast-track the scheme.
But she warned that it was currently "not the time to travel", and that the more responsible people are now "the more possibilities we will have to spend a normal summer".
While Dublin MEP Barry Andrews has previously suggested that UK cooperation in the scheme would be important, as Ireland is outside the EU Schengen Area.
"The crucial part for Ireland of course is that the UK is included in whatever is proposed by the European Union", he said.
"Let's have it now, let's set it up now, let's make sure that there's some kind of summer.
"If we have a widespread vaccination campaign, it also has to be combined with normal handwashing, test and trace, mask wearing and all of the hygiene elements in order to get some kind of a tourism season back up and running."
And executive director of the Irish Council for Civil Liberties (ICCL) Liam Herrick said he believes this could be made difficult because of a slow vaccine rollout or transmission worries.
He told Newstalk earlier this month: "There are two aspects to the issue of vaccine or immunity certificates, one is the question of travel and that's a complex one because we're waiting at this stage for the EU detail.
"Certainly it's possible for states to require certificates of immunity in some circumstances but really the devil will be in the detail.
"A separate question is that some countries, for example, Israel, have introduced immunity or vaccine certificates within the state in terms of access to goods are services.
"We think that is wholly inappropriate and it would lead to a two-tier society, especially when there's a shortage of vaccine so we think this is an opportunity for the Government to come out and say it opposes that, he added.
Additional reporting: IRN