I concur with many of the fellow cruiser enthusiasts' responses. I found this article about why is travel insurance important when going on a cruise (https://www.travelinsurance.ca/en_CA/travel-tips/cruise-travel-essentials/travel-insurance-for-cruising.html). Usually many cancellation policies cover cancellation due to an unforeseen event such as sickness and by having the doctor clearly stating/advising the patient not to travel.