Royal Caribbean International announced this week that it would suspend cruise bookings until early January due to capacity limits.

“Glider flights starting by early January 2022 are no longer open to new reservations as they have reached the limited capacity we have set,” said Vicki Freed, Senior Vice President of Sales and Trade Support and Service, Royal Caribbean: according to USA Today.

Several COVID-19 clusters have been reported on Royal Caribbean cruise lines in the past few days. On Thursday, Odyssey of the Seas reported 55 cases and Symphony of the Seas reported 48 positive COVID-19 cases after disembarking last Saturday, the news agency noted.

Medical staff and crew on the ships were “overwhelmed” by the increase in cases, passengers told USA Today, although Royal Caribbean denied this characterization.

Royal Caribbean said the capacity limits were implemented as part of “robust, layered protocols,” USA Today reported.

On Friday, the cruise company sent passengers a notice stating that the mask requirement on board ships would be tightened until January 5th.

“Given the recent surge in COVID-19 in the world and additional concerns about the Omikron variant, we feel it advisable to temporarily tighten our onboard health protocols to require masks indoors at all times unless actively eating or drank, “said Freed, according to USA Today. “This new update also applies to vaccinated areas and venues.”