Federal health officials are dropping the warning they have attached to cruising since the beginning of the pandemic, leaving it up to vacationers to decide whether they feel safe getting on a ship.

Cruise-ship operators welcomed the announcement, which came as many people thought about summer vacation plans.

An industry trade group said the move by the Centers for Disease Control and Prevention last Wednesday validated measures that ship owners have taken, including requiring crew members and most passengers to be vaccinated against the virus.

The CDC removed the COVID-19 “cruise ship tr...