Holland America Line and Seabourn have become the latest Carnival Corporation brands out ease Covid-19 protocols.
The changes cover cruises from September 6, alongside other lines such as UK-based P&O Cruises and Cunard and Carnival Cruise Line and Princess Cruises.
Testing for fully jabbed passengers will be dropped for most sailings of less than 16 nights in duration.
Unvaccinated travellers will only need to submit a self-administered test taken within three days of sailing.
However, the eased protocols do not apply to itineraries for countries where local regulations may vary including Canada, Australia and Greece.
Passengers on cruises of 16 nights or more, not including transits of the Panama Canal, must submit a medically supervised Covid-19 test with a written negative result taken within three days of embarkation.
They must be vaccinated or request an exemption.
Holland America Line president Gus Antorcha said: “Our guests have been excited to return to cruising, and these changes will make it easier for more guests to explore the world in a safe and enjoyable environment.
“The new, simplified protocols recognise the evolving nature of Covid-19 while still ensuring we protect the health of our guests, team members and the communities we visit.”
Seabourn president Josh Leibowitz added: “Our goal is to offer a luxury vacation experience that is unmatched in quality, safety, and joy.
“These updated guidelines reflect our ongoing commitment to protecting our guests, the people in the communities we touch and serve, and our shipboard and shoreside employees.”