Infectious diseases lay a heavy burden upon public health in many parts of the world. The toll they take in terms of human suffering, social hardship, and economic cost is huge and as a consequence, preventing and combating them are keys to the development of the most affected regions. A number of these diseases are, fortunately, vaccine preventable and the introduction of vaccination is one of the greatest achievements and most cost-effective interventions in public health that have ever been made. The health impact of current vaccination programmes is tremendous and perhaps only surpassed by the effect of measures to prevent poverty and to introduce clean water and well-functioning sanitation for all.