Corrections & clarifications: This story has been updated to reflect that though Celebrity Cruises has billed the Celebrity Millennium sailing as “fully vaccinated,” some unvaccinated children are aboard the ship. 

Two passengers from the United States who shared a room on board Celebrity Cruises’ Celebrity Millennium ship, which was billed as carrying “fully vaccinated crew and guests”, have tested positive for COVID-19, .

The tests came back positive during end-of-cruise testing, which is completed 72 hours before passengers return to the U.S., Celebrity Cruises spokesperson Jonathon Fishman told USA TODAY. 

All adult passengers were required to show proof of vaccination in addition to a negative COVID-19 test within a 72-hour period before the ship departed from the Caribbean island of St. Maarten Saturday.