Are immunizations necessary?

If taking a cruise to the Panama Canal (with port stops in Cartagena and Limon), is it necessary or recommended to get immunizations for yellow fever or typhoid?

No, I don't think yellow fever and typhoid immunizations are recommended or required. If you will be doing on the ground travel in other regions of the world where those diseases are more common then getting the immunizations before your trip would not hurt but I would not get the shots just for this trip.

If you want to get shots I'm big on the annual flu shot and hepatitis immunizations. Hep immunizations are something that can help protect you all over the world.