Yes, there are no new protocols based on the existence of vaccines. That's because the Conditional Restrictions protocols are still in effect and are sufficient to restart cruises based on the reality that a portion of cruise line guests will *not* be vaccinated.
But, since last November, cruises could still have happened if cruise lines followed the Conditional Restrictions. As far as I can tell, before vaccines, I can't find any reference to a list of further protocols that cruise lines were waiting for. The Conditional Restriction made it clear: Follow the COVID hygiene protocols. These are the same ones states and businesses implemented: reduced capacity, plexiglass, masks, distancing, ventilation, sanitization, etc... The Conditional Restrictions expected the cruise lines to implement these sensible protocols and do a practice run to show the CDC they're working. There is, AFAIK, no other protocol document that the cruise lines are waiting for under the current Conditional Restriction. If someone claims there is, they need to provide that link.
The big news in cruising is that the CDC has taken the step of letting the 'No Sail Order' expire. But it's not back to sailing just yet. Replacing the ban on sailing is a 'Framework for Conditional Sailing Order.' That framework lays out in detail what the CDC requires cruise lines to do to...
www.cruzely.com
Now, if you claim there should be a new Conditional Order, one that takes into account vaccinations. That's a different story. If cruise lines are waiting for that mythical beast... they're choosing to hold off cruising in order to avoid the current Conditional Order.
They want a pain-free return to cruising with everyone vaccinated. But everyone won't be vaccinated fully (second dose plus two weeks) until mid-June. And even then, children won't be vaccinated. So, unless cruises are willing to run adult-only, vaccine-passport cruises, the current Conditional Order will stand until children are vaccinated (or herd immunity practically wipes out all cases). That's not happening until the Fall (I would guess).