Austria and Israel have reportedly become the first two countries to impose a time limit on the validity of vaccinations, unless travellers have boosted their immunity with follow-up doses.

Vaccinated travellers will have to abide by Austria’s entry rules for unvaccinated arrivals unless they have had a booster within 360 days of their second dose - which means they will have to pay for a Covid test to enter.

Israel will only allow visits if holidaymakers leave the country no more than 180 days after their second dose, the Telegraph reported.

Travellers can enter the country if they have "received a booster dose and at least 14 days have passed by the day of entry" 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 reportedly be allowed in.