Travelers are being urged to check the rules before they travel abroad this summer after some people vaccinated in Estonia experienced problems on arrival.
Currently, every country has its own travel rules in place which can create confusion for travelers.
In some cases, countries only count a person as fully vaccinated if they have had two doses of vaccine and may say they need to quarantine on arrival. But in Estonia someone who has recovered from coronavirus only needs one "booster" dose and they are then considered fully vaccinated.
Lauri Koost from the travel agency Nautilus Travel said some people have experienced this problem.
"We received information that a passenger was vaccinated under Estonian law with one dose of a vaccine that would otherwise require two doses. After arriving in the country of destination, the healthcare professional found that the passenger had received one dose and was not exempt from the restrictions for vaccinated people who have received two doses. In the future, there may be a plan or plan for passengers who receive one dose so that they receive another dose."
Irja Lutsar, professor of virology at the University of Tartu and head of the government's scientific advisory council, said those who have recovered do not need a second dose of vaccine.
"We've seen that this one dose gives a very high antibody concentration. One dose works like a booster dose. A lot of countries agree. Unfortunately, yes, it's a situation where each country has made its own rules."
Tiina Kallasmaa, director of the Consular Assistance Office of the Ministry of Foreign Affairs, said everyone must carefully read the rules of destination and transit countries in order to travel hassle-free this year.
It is hoped problems will be reduced now that the EU's digital certificate has come into force.
Aurora Ursula Joala, adviser of the Ministry of Social Affairs in the field of e-services development and innovation, said: "The purpose of the digital certificate is to provide three different types of evidence in accordance with uniform standards in the European Union: an immunization certificate, a negative test certificate and travel pass certificate."
Editor: Helen Wright