1. The child presents with abdominal pain, fever, and decreased appetite for 13 days. Examination finds a coated tongue.
2. The most likely diagnosis is enteric fever. Investigations include blood culture, Widal test, and bone marrow culture. Complications are intestinal hemorrhage, perforation, encephalopathy, and sepsis.
3. There is a typhoid vaccine of purified Vi antigen in a single 0.5ml dose with booster doses every two years.