We just came off the Serenade and were actually surprised to see no sign of hand sanitizers anywhere. That was until the second last day when, as we were getting back on the ship in Barbados they were everywhere. No entry to the dining rooms or Windjammer without using one first. The cabin stewards started wearing masks and all of the handrails were constantly being cleaned.
I am not sure why the hand sanitizers do not stay out all of the time. It seems that prevention would be cheaper than treatment.
That said I agree with Sonny, if you are looking to get sick you will. All it takes to remain healthy is a little common sense.