Multiple passengers and crew members who were fully vaccinated have tested positive for COVID-19 onboard a Princess Cruises' ship that was headed to the Panama Canal on a 15-day voyage.

The Ruby Princess ship had a 100% vaccination rate for both passengers and crew members, Princess Cruises said, according to Los Angeles Times. Passengers were required to have a negative COVID test as well as proof of vaccination prior to boarding the Ruby Princess cruise ship.

The infected passengers and crew were isolated and quarantined after testing positive for the virus. All were either asymptomatic or showing mild COVID-19 symptoms, the cruise line said, as reported by KTVU, a Fox affiliate out of San Francisco.

It was unclear at the time exactly how many passengers and crew members onboard the Ruby Princess ship had tested positive for COVID-19 or how far along in the sailing the ship was at the time the infections were discovered.

According to Princess Cruises, passengers on the ship who had tested positive for the virus and had not completed the full isolation period were allowed to return home or were put up in hotel rooms for the rest of the isolation and quarantine time, the Los Angeles Times reported.

The Centers for Disease Control and Prevention has dropped cruise ship travel to its Level 2 “moderate” risk category for contracting COVID-19 after it spent a significant amount of time sitting in its Level 4 “very high” risk category.

Princess Cruises, along with the rest of the U.S. cruise industry, suspended its sailings for more than a year during the pandemic to help prevent the spread of the virus as cruise ships were seen as superspreaders of the virus.

The Ruby Princess cruise ship did return to the Port of San Francisco on Sunday and has already departed for a 15-day sailing to Hawaii, Los Angeles Times said. The Port of San Francisco requires that at least 95% of all passengers and crew be fully vaccinated.

The Grand Princess belongs to Princess Cruises, the same company which operated the coronavirus-stricken ship held off Japan last month on which more than 700 people on board tested positive The Grand Princess belongs to Princess Cruises, the same company which operated the coronavirus-stricken ship held off Japan last month on which more than 700 people on board tested positive Photo: INTERPRESS / STRINGER