The expanded programme on immunization: a lasting legacy of smallpox eradication.

Since the mid-1970s, the widespread establishment and implementation of the Expanded Programme on Immunization (EPI) has led to remarkable achievements in controlling vaccine preventable diseases worldwide. Today, more children than ever are being reached with immunization; interruption of poliomyelitis transmission has occurred in most countries; mortality due to measles, tetanus, diphtheria and pertussis has been reduced to record low levels. In addition, increasing numbers of vaccines are being used for infants and older age persons, such as vaccines against hepatitis A and hepatitis B, Haemophilus influenzae type b, rotavirus, pneumococcus, meningococcus, human papilloma virus (HPV) and varicella. The design of EPI reflects in large part the experience accumulated during the implementation of the intensified campaign for smallpox eradication during the period 1966-1977. At that time, the existing health infrastructure and network was found inadequate to reach most individuals with community wide immunization programmes in most countries. Thus, efforts were made to train dedicated health personnel and allocate specific resources for programme coordination and implementation. With the establishment of EPI, there was a gradual shift in emphasis from vaccination campaign strategies using mobile teams to the delivery of immunization services as part of routine health services of health facilities. Both the campaign and the outreach strategies are nevertheless required to reach those segments of the population not reached by the routine health services and to accelerate the achievement of disease control initiatives such as polio eradication and measles elimination. Whilst the campaign for smallpox eradication was set up as special and time-limited effort, the EPI requires long-term sustainable approaches to protect new cohorts of susceptible persons with vaccination and monitor trends and progress towards disease control with high quality surveillance.