Silversea Cruises is the latest cruise operator to require fully vaccinated ships.
It means only vaccinated guests will be allowed aboard.
Silversea said the requirement is for all cruises except in Australia. It said it is still evaluating protocols for Australia.
Other cruise lines including sister brands Royal Caribbean and Celebrity Cruises have implemented mandatory Covid-19 vaccination policies.
"Vaccinations will play a critical role in ensuring the health and safety of our guests, crew, and the communities we visit. We have introduced a range of initiatives including our ‘Cruise with Confidence’ program and our Covid-19 protections," said Roberto Martinoli, President and CEO of Silversea Cruises.
Flagship Silver Moon will start operations on 18 June on 10-day itineraries to the Eastern Mediterranean from Greece.
Scheduled port calls include Santorini, Mykonos, Crete, Haifa and Cyprus.
