The answer is yes. And there is no vaccine available against malaria, but the good news is that there are prophylaxes you can take. As it is better to avoid getting sick than to cure we recommend the use of anti-malarial medication when visiting Zanzibar. It is best to make an appointment with a travel medical specialist who can advice you best.
Malaria is an infectious disease that is caused by a parasite. You get it from the bite of a mosquito that carries the parasite. These parasites multiply first in the liver cells and then in the red cells of the blood. The symptoms include shaking chills, followed by fever, usually preceded by flu-like illness.
To protect yourself against mosquito bites, you can spray yourself with insect repellent containing DEET and make sure to cover your body properly if you are outside after sunset.