From MSC's US site for Med:
https://www.msccruisesusa.com/health-and-safety-measures/mediterranean
COVID-19 TEST REQUIREMENTS:
All fully COVID-19 vaccinated guests 12 years and older are required to show proof of a negative antigen or RT-PCR test taken no more than 2 days before embarkation. Guests must bring the valid negative test certificate with them to the terminal. MSC Cruises may provide additional testing, if necessary, at the terminal during embarkation or on board to protect our guests and crew.
To note: An antigen self-test is not accepted for embarkation.
Requirements for fully vaccinated guests under 12 years old are the same as testing requirements for guests 12 years and older who are fully vaccinated.
All guests not fully vaccinated (all guests under 12 years of age, given our vaccination requirements) are required to show proof of a negative RT-PCR test taken no more than 2 days before embarkation. Guests must bring the valid negative test certificate with them to the terminal.
These guests may undergo an additional COVID-19 test at the terminal prior to embarkation provided by MSC Cruises, free of charge. The only exception is that no pre-embarkation or embarkation testing is required for guests under 2 years of age.