The positive tests occurred even though all adult guests were required to show proof of vaccination before boarding the ship and that all guests had to provide a negative COVID-19 test within three days of coming aboard the vessel.
The positive tests came aboard the Celebrity Millenium, a ship operated by Royal Caribbean's Celebrity Cruises. The ship, which set sail June 4, has one more day at sea before returning to the Caribbean island of St. Maarten for disembarkment.
CNN and the NYT report that the guests, who shared a stateroom, tested positive on a COVID-19 test that all guests were required to take before heading home. The New York Times reports that the passengers are asymptomatic, in isolation and under observation by a medical team.
CNN reports that 95% of 500 guests aboard the Celebrity Millenium were fully vaccinated. Children, who are not yet approved to be vaccinated, were allowed on board so long as they tested negative for the virus.
The news comes as the U.S. cruise industry prepares to resume business. The New York Times reports that Celebrity Edge will set sail out of Fort Lauderdale, Florida on June 26 with all crew and 95% of passengers fully vaccinated.
While COVID-19 vaccines have proven to be safe and effective, it's still possible — though extremely rare — for fully vaccinated people to contract the virus.
According to data released by the Centers for Disease Control and Prevention in May, about .01% of fully vaccinated people have contracted the virus. Of that .01%, the vast majority were asymptomatic.