Carnival Corp's major cruise lines will drop mandatory COVID-19 testing for vaccinated guests and allow unvaccinated passengers to travel without an exemption in some cases, the company said on Friday.

The decision affects Carnival Cruise, Princess Cruises and Cunard and follows a similar move by rival Norwegian Cruise Line Holdings Ltd earlier this week.

Unvaccinated guests - who still have to present a negative COVID-19 result - no longer need to apply for an exemption except for Carnival Cruise's sailings in Australia or on its voyages 16 nights and longer.

The cruise industry has in recent months bounced back from an over one-year-long pause in sailings due to the COVID-19 crisis, but rising inflation and labor constraints pose risks to its outlook.