The U.S Centers for Disease Control and Prevention (CDC) issued updated guidance on Friday that said people who are at high risk of severe complications from COVID-19 should avoid cruise ships.

“People with an increased risk of severe illness should also avoid travel on cruise ships, including river cruises, regardless of vaccination status,” the agency said, in an updated page on its website.

The CDC also noted that people who are not fully vaccinated should avoid cruising.

In addition, the CDC said people on cruise ships should wear a mask to keep their nose and mouth covered when in shared spaces.

“While CDC’s Mask Order is not being enforced on cruise ships, individual cruise lines may require travelers (passengers and crew) to wear masks indoors on board the ship,” it said.