Vaccination for Yellow Fever is required for several countries in Africa and South America and recommended for others. Travel clinic can advise you which city/country carries a risk for Yellow Fever. Yellow Fever is special live vaccine with several precautions and contraindications and should be taken at least 10 days before departure.
Yellow Fever can only be given by the Health Canada approved vaccination centres.
There may be several other risks such as Rabies, Polio, Tick Borne Encephalitis and Japanese Encephalitis to the travellers; those can be discussed by the travel medicine consultant depending upon your particular destination.