ne question asked by those who doubt the efficacy of vaccination is whether improvements in general health could explain the reduction in incidence and severity of diseases like measles and whooping cough. This doubt is countered by those who advocate vaccination by pointing to the experience that these diseases can, and will, re-emerge with fatal cases if vaccination levels fall. Measles is one of the best examples of this debate. Whooping cough gives a historical perspective to the debate on vaccine efficacy, while outbreaks of mumps are topical. Diphtheria, poliomyelitis and Haemophilus influenzae type B (Hib) are give further examples of how important surveillance is to ensure that vaccines are used to best effect.