Washington, Dec 31 (IANS): The US Centers for Disease Control and Prevention (CDC) has called on people to avoid cruise travel, regardless of vaccination status, as more Covid-19 cases driven by the Omicron variant have been identified on cruise vessels.

"The Covid-19 Travel Health Notice level has been updated from Level 3 to Level 4, the highest level. This reflects increase in cases onboard cruise ships since identification of the Omicron variant," said the CDC.

Even fully vaccinated travelers may be at risk for getting and spreading Covid-19 variants, the agency added.

"The virus that causes Covid-19 spreads easily between people in close quarters on board ships, and the chance of getting Covid-19 on cruise ships is very high, even if you are fully vaccinated and have received a Covid-19 vaccine booster dose," said the CDC.

It is especially important that travelers who are at an increased risk of severe illness from Covid-19 avoid travel on cruise ships, including river cruises worldwide, regardless of vaccination status, the agency added.

A total of 88 vessels are under CDC's investigation or observation for Covid-19 outbreaks. Four other vessels are also being monitored by the CDC, according to data released on the agency's website on Wednesday, Xinhua news agency reported.