The updated recommendation came from the US Centre for Disease Control and Prevention (CDC) on Friday (20 August).
Those with an increased risk of severe illness, regardless of vaccination status, and those who have not been fully vaccinated have been advised to avoid travel on cruise ships, including river cruises, worldwide.
The CDC warned it may adjust requirements and recommendations on its phased approached to returning US cruise ships back into operation "based on public health considerations and other factors".
Cruises are currently ranked level three in the CDC’s list of Covid risk levels.
