Vaccine impact: Benefits for human health.

Unlike most drugs, whose benefit is restricted to the individual who takes the drug, prophylactic vaccines have the potential for far-reaching effects that encompass health service utilisation, general health and wellbeing, cognitive development and, ultimately, economic productivity. The impact of immunisation is measured by evaluating effects directly on the vaccinated individual, indirectly on the unvaccinated community (herd protection), the epidemiology of the pathogen (such as changing circulating serotypes or prevention of epidemic cycles), and the additional benefits arising from improved health. Aside from protection of the individual, the broader success of immunisation is dependent on achieving a level of coverage sufficient to interrupt transmission of the pathogen. When evaluating the cost-effectiveness of vaccines, all of these potential benefits need to be accounted for. In many countries where immunisation programmes have been highly successful, the control of disease has meant that the benefits of immunisation have become less obvious. Once a well-known and much-feared disease appears to have disappeared, individuals, including healthcare professionals, no longer view ongoing prevention with the same sense of urgency. Reduced coverage is inevitably associated with resurgence in disease, with outbreaks potentially leading to significant morbidity and loss of life. Ensuring the continued success of immunisation programmes is the responsibility of all: individuals, healthcare professionals, government and industry.