Immunisation prevents two to three million deaths worldwide every year from diseases such as diphtheria, tetanus, pertussis (whooping cough) and measles. Millions more are spared the long-term health consequences of vaccine-preventable infectious diseases; the WHO estimates that due to the Global Polio Eradication Initiative, five million people are walking today who would otherwise have been paralysed by the virus.

In Europe, one of the greatest barriers to the wider uptake of immunisation is distrust, among some sections of the public, of immunisation programmes. This is due largely to fears surrounding vaccine safety. In fact, serious side effects are very rare. Nevertheless, as vaccines are given to healthy people, public acceptance of the risk of any adverse reaction is much lower than for medicines designed to treat sick people; the trade-off between benefit and risk is different.

Vaccines undergo rigorous safety testing before they are approved for public use. Currently, efforts to monitor the coverage, benefits and risks of vaccines after approval are rather fragmented.

At the same time, some vaccines have been around for so long that many people have no personal experience of the diseases prevented, and so are unaware of just how serious the illness can be.