Typhoid vaccination. First typhoid vaccination, photographed at the United States Army Medical School. The doctor on the right is vaccinating a student, while the doctor at centre right is filling a syringe. Typhoid is an infection of the digestive system caused by the bacteria Salmonella typhi. It is transmitted through infected food and water. It causes high fever, diarrhoea and a rash. Severe infections can include inflammation of the spleen and bones, delirium and erosion of the intestinal wall. Vaccinations involve exposing the body to dead or weakened disease- causing micro-organisms, strengthening the immune system against future infection.