Transmission
Typhoid spreads through food and water contaminated with Salmonella Typhi bacteria — typically in regions where sanitation is limited. Risk is highest with unfiltered tap water, ice cubes, raw salads and shellfish.
Geography
Endemic across the Indian Subcontinent (India, Pakistan, Bangladesh, Nepal), sub-Saharan Africa, Southeast Asia and parts of Latin America. India alone reports ~3M cases per year — UKHSA recommends vaccination for any trip over a week in endemic regions.
Immunity
A single dose of TYPHIM Vi gives around 70% protection from 14 days, lasting about 3 years. Boosters are needed every 3 years for ongoing exposure. The vaccine does not protect against paratyphoid.