Since Edward Jenner's breakthrough in 1796, vaccination has probably saved as many lives as any other public health innovation, with the exception perhaps of improvements to sanitation and water safety. Without vaccines, global eradication of smallpox and elimination of poliomyelitis and measles from large parts of the world would have been impossible. These achievements have been accomplished largely with vaccines delivered through a global system, the Expanded Programme on Immunization (EPI), which has received sustained support for more than 30 years from national governments, donor organisations, and international agencies such as UNICEF and WHO. However, diseases such as pneumonia, diarrhoea, meningitis, and measles, which are currently preventable by vaccination, still account for about a quarter of child deaths in low-income countries (figure 1).1, 2, 3, 4 In adults, tuberculosis and cancers of the cervix, liver, and some other sites are also potentially preventable by vaccination and, yet, continue to cause much suffering and many deaths. With these past successes, rapid advances in biomedical sciences, and a delivery system that reaches nearly all children at least once in the first year of life, we have high expectations that new vaccines will further improve global health.
Three major challenges exist to enhancement of current success in prevention of infectious disease by vaccination. First, we need to further expand coverage of existing vaccines, such as those against diphtheria, tetanus, and measles. Second, effective new vaccines need to be implemented widely, such as those against Haemophilus influenzae type b and pneumococcal, meningococcal, rotavirus, and human papillomavirus infections. Third, we need to develop new vaccines against important pathogens, such as malaria parasites and HIV, for which no effective licensed vaccine yet exists. Here, in the fourth paper of this Series, we focus mainly on the first and second challenges with respect to low-income and middle-income countries, because these areas are where the main challenges to introduction of new vaccines are found and where characterisation of policies, programmes, and financing necessary for further progress is most urgent. However, some issues discussed by us here are also relevant to high-income countries.
Key messages
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Access to vaccines for children in developing countries began to expand rapidly in the mid-1970s, with establishment of the Expanded Programme on Immunization, and has subsequently prevented many millions of deaths and illnesses
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Immunisation programmes need ongoing review to account for changes in the epidemiology of major infectious diseases and availability of new vaccines
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Vaccination policies should be based on solid evidence and rigorous science; efforts are underway to ensure that all countries have an established body that can make evidence-based decisions about vaccine policy
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Experiences with new vaccines, such as pneumococcal and rotavirus vaccines, have shown that vaccine access for children in developing countries can be accelerated, but this process needs to be improved further to meet the needs of new vaccines on the horizon
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Sustainable predictable financing is likely to be a major ongoing challenge to achievement of universal access to all vaccines; innovative ways are being developed to tackle introduction of pneumococcal and rotavirus vaccines, but financing of other new vaccines, which are likely to be at least as expensive, remains to be established
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Continued vaccine research is needed to keep safe, effective vaccines in the pipeline
Recently developed vaccines, and some of those likely to arrive soon, share many characteristics. In general, they are substantially more complex and expensive than vaccines that preceded them. The new pneumococcal conjugate vaccines, for example, are combinations of ten or 13 individual vaccines and nearly a year is needed to manufacture one batch. Finding ways to ensure that these new vaccines are available and accessible to populations that most need them is a major challenge to the international community.