Communications regarding Covid-19 and variants are constantly changing. What might have been the guidance from the Centers for Disease Control and Prevention (CDC) “last week” is likely not the case “today.” Your best information will be found directly on the CDC website itself. The current guidance from the CDC for cruise ships is here.
You can also check directly with the cruise line on which you’re sailing, or the trusted travel advisor through whom you made your reservations can also help you. One thing that has not changed, and is unlikely to for some time, is the requirement that travelers be vaccinated and show proof of the vaccination (and possibly even the booster shot). This is not only a requirement of cruise lines, but also for most countries where the cruise lines visit (which is why the cruise lines have the requirement).