Emergency typhoid immunisation after the fall of Singapore 1942.

Singapore surrendered to the Japanese invasion in February 1942 after its water supply collapsed. At the suggestion of the colonial medical authorities, an emergency typhoid immunisation campaign was then begun using locally manufactured vaccine from extemporary materials; within 3 months, >600 000 had been immunised. Comparison with prewar statistics suggests that a postsurrender typhoid fever epidemic was prevented despite an increase in other enteric infections. Public health crises with disrupted supply chains may make locally manufactured vaccines of increasing importance in the future.