Those affected onboard Ruby Princess ship were either asymptomatic or showed mild COVID symptoms and were isolated and quarantined. The company didn't say how many had tested positive.
The ship has since departed homeport San Francisco for a 15-day roundtrip to Hawaii.
Princess Cruises requires passengers to show a negative COVID test and proof that they were fully vaccinated at least 14 days prior to departure. Vaccination rates for guests and crew on Ruby Princess were at 100%.
Port San Francisco also requires that at least 95% of both passengers and crew onboard are vaccinated.
The company said guests with positive tests who had not completed the required isolation period had returned back home or were provided hotel rooms for quarantine.
For more Ruby Princess incidents and accidents see the ship's CruiseMinus page.