Holidaymakers face travel restrictions if they have not had booster Covid jabs.

Austria and Israel have become the first two countries to impose time limits on the validity of vaccinations – unless travellers have boosted their immunity with follow-up jabs.

Austria will treat jabbed travellers as unvaccinated unless they have had a booster within 360 days, or just under 12 months, of their second dose. This means they will be required to pay for a Covid test to secure entry.

Israel has even tougher rules. It allows visits only if the holidaymakes leaves the country no more than 180 days after their second dose.

Travellers can enter the country if they have “received a booster dose and at least 14 days have passed by the day of entry into Israel,” the rules state.

As a result, many triple-jabbed British travellers face being excluded – though people who have proof of recovery from Covid within the previous 190 days, or six months, will be allowed in.

Paul Charles, the chief executive of travel consultancy The PC Agency, believed other countries could follow Austria and Israel’s example. “It’s likely countries will continue to ensure we are fully jabbed. By fully jabbed that means being up to date. We are seeing countries starting to align,” he said.

Another travel chief warned the disparate strategies of different countries were undermining the revival of flying. “There’s going to be alignment problems around countries’ vaccine approaches,” he said.

“There needs to be international agreement around this. The Government talked about having an internationally agreed approach at the G7 earlier this year but we have seen nothing come from that.

“It is a relatively strange approach that these countries are taking on the booster jab but what we are seeing is that disparate strategies on vaccines are undermining travel.”