Travelers, regardless of vaccination status, have been advised not to vacation on cruise ships amid the global rise in COVID-19 cases, according to the Centers for Disease Control and Prevention.

The CDC’s updated COVID-19 Travel Health Notice rose from a level three to level four, the highest warning level, as the omicron variant makes its way through the United States, according to a statement from the agency. Even vaccinated and boosted people risk spreading the coronavirus on cruise ships.