Norwegian Cruise Line Holdings will continue to follow the Centers for Disease Control & Prevention (CDC) conditional sailing order, although the US agency will deem such adherence voluntary as of Saturday.

The New York-listed owner of 28 ships announced on Friday that Norwegian Cruise Line, Oceania Cruises and Regent Seven Seas Cruises will uphold what the CDC now calls the "Covid-19 Program for Cruise Ships Operating in US Waters".

Chief executive Frank Del Rio said Miami-based Norwegian has shown full commitment to the conditional sailing order, which was extended by almost three months in late October, by requiring vaccinations for all passengers and crew since July.