Depends where you are going... In Canada we are recommended to get the Twinrix Vaccinations if we are travelling to Mexico or the Caribbean etc. (regardless of whether you are cruising or not).
I just had my first shot and I am assured that I will well protected after my 2nd shot just before we leave... the third is a booster given atleast 6 mos after first.
The Centers for Disease Control recommends vaccinations and/or medicine against the following illness for travellers.
Hepatitis A, which is spread by the fecal-oral route, person to person or through contaminated water or food. It is the second-most common infection in travellers and the number one vaccine-preventable illness among travellers.
Hepatitis B , especially if you might be exposed to blood or body fluids, have sexual contact with the local population, or be exposed through medical or dental care, skin cuts and abrasions (which can happen pretty easily while on holiday even though unplanned), aesthetic services involving reusable instruments, or injection drug use.