Just got off Zaandam VOV. First cases started to show up 2 days into the trip and they rapidly ran out of quarantine rooms on deck 6. After that they quarantined you in your room for minimum of 6 days. Were not requiring masks be worn until the number of cases appeared to be well over 100 and it became a strain on things like room service. When they required masks on tenders and inside the ship the number of cases began to fall. Of course some experts cheated by removing masks in the showroom once the lights went out. Childish.
Good news was that none of the cases we heard about seemed severe so score one for the vaccines. (There were 3 medical evacuations but no idea what for and it was a VERY old demographic even by HAL standards)
As soon as the mask requirement was eliminated on the way back they started to report new cases. Interesting results from a closed population experiment.
I think the testing requirement before a cruise sounds good but in reality is likely to miss some folks in the early stages and, with no other controls once onboard, it spreads rapidly. On the other hand, eliminating the vaccine requirement seems to be asking for trouble with a severe case not being able to be tended to onboard.
Regardless of what they require we will continue to wear masks inside take the boosters when available and probably skip the tenders altogether. Just my observations after a longer voyage.