In a letter to the cruise industry, the CDC has stated that operations may resume as soon as Mid July, with 95% vaccinated passengers.
In Series of clarifications, the CDC is making it much less burdensome to resume cruising:
In Clarification #1stated that "test Cruises" could be bypassed If 98% of Crew, and 95% of Passengers are vaccinated.
the 2nd clarification dropped the review process for test cruises has dropped from 60 days, down to 5 days.
The 3rd Clarification dropped the PCR test, in favor of a rapid antigen test, and aligned quarantine procedures with interstate travel
The 4th clarification dropped the Single-Port agreement requirement
The 5th Clarification allows for local passengers to drive home, and airline passengers to quarantine in a hotel in the event of a COVID-19 outbreak.
Source: