Two major infections, smallpox and rinderpest, have been eradicated. Global coverage of vaccination against many important infectious diseases of childhood has been enhanced dramatically since the creation of WHO's Expanded Programme of Immunization in 1974 and of the Global Alliance for Vaccination and Immunization in 2000.
The story of the eradication of smallpox is described by Henderson, who played a key role in the eradication campaign, in his book ‘Smallpox—the eradication of a disease’, which sets out the challenges that the eradication team faced and how these were met: important lessons for today [4].
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Herd immunity is the population-level consequence of acquired immunity among some individuals that can reduce the risk of acquiring infection among susceptible individuals. Individual immunity can be acquired either through a natural infection or through artificial inoculation with a vaccine.
First, there is extreme heterogeneity in the risk of acquiring and transmitting the infections. Second, the diseases affect sexually active adults, and severe disease often is restricted to a minority of cases, with the majority of severe consequences affecting women rather than men. These factors will influence the effects of herd immunity and the target populations to be protected by vaccination programs
Two types of efficacy are illustrated: “take” type, in which the vaccine either does or does not protect an individual, and “degree” type, in which all those vaccinated are protected from a fraction of challenges . Effect of herd immunity on the spread of an infection in a homogeneous population.
Two major infections, smallpox and rinderpest, have been eradicated. Global coverage of vaccination against many important infectious diseases of childhood has been enhanced dramatically since the creation of WHO's Expanded Programme of Immunization in 1974 and of the Global Alliance for Vaccination and Immunization in 2000.
Firstly, the disease has distinctive clinical features; secondly, it was well recognized and much feared in the communities where it was prevalent; and finally , and perhaps most importantly , sub-clinical infections were rare.
Because EPI vaccines are relatively cheap when mass produced, full immunization of a child cost around $15 in the 1990s.
An alternative way of making microorganisms safe for use in a vaccine is to kill them, and at the beginning of the twentieth century a number of vaccines based on killed whole organisms, including the pneumococcus, meningococcus and typhoid bacillus, were developed and used.
The story of the eradication of smallpox is described by Henderson, who played a key role in the eradication campaign, in his book ‘Smallpox—the eradication of a disease’, which sets out the challenges that the eradication team faced and how these were met: important lessons for today [4].
1. Introduction. It is often stated that vaccination has made the greatest contribution to global health of any human intervention apart from the introduction of clean water and sanitation, but this is a claim that needs some qualification.