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South African Medical Journal

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Pneumococcal conjugate vaccine – a health priority

HJ Zar, SA Madhi

Abstract




Pneumonia is a major cause of childhood mortality and morbidity. Streptococcus pneumoniae is the most important bacterial pathogen causing pneumonia in children. The HIV epidemic has increased the burden and severity of childhood
pneumococcal pneumonia and invasive disease fortyfold. Pneumococcal conjugate vaccine (PCV) is a highly effective intervention to reduce invasive pneumococcal disease and
pneumonia. Studies evaluating a 9-valent PCV in South Africa and The Gambia reported a 72 - 77% reduction in vaccineserotype- specific invasive disease in vaccinated children.
As many of the pneumococcal serotypes associated with antibiotic resistance are included in PCV, vaccination has also been associated with a reduction in antimicrobial-resistant
invasive disease. PCV may also reduce childhood mortality, especially in places with limited access to health care, as shown in Gambian study in which PCV reduced childhood
mortality by 16%. In addition to the direct effects of PCV, there is a substantial reduction in disease burden through indirect protection of non-vaccinated populations.
PCV is immunogenic in HIV-infected children and provides protection against invasive disease or pneumonia in a substantial number of children. Although the efficacy of PCV
for prevention of invasive disease or pneumonia is lower in HIV-infected compared to -uninfected children, the overall burden of disease prevented is much greater in HIV-infected
children because of the higher burden of pneumococcal disease in these children. Consequently, vaccine-preventable invasive disease is almost 60 times higher in HIV-infected compared to -uninfected children, while the reduction in pneumonia in HIV-infected children is 15 times greater. However, the long-term efficacy of PCV wanes in HIVinfected
children who are not taking antiretroviral therapy, and booster doses are probably indicated. Although there is concern about the potential for replacement disease due to non-vaccine serotypes, a substantial and sustained reduction in invasive disease has
occurred overall in populations with widespread childhood immunisation. Routine childhood immunisation is now the standard of care in most developed countries. However, PCV
is much less accessible to children in developing countries due to cost and availability. Cost-effectiveness analysis indicates that use of PCV is potentially highly cost-effective,
at tiered pricing, even in very low-income countries. Widespread availability and vaccination with PCV is urgently needed for all children under 2 years of age in South Africa. In addition, the use of PCV for all HIV-infected children under 9 years should be prioritised.

South African Medical Journal Vol. 98 (6) 2008 pp. 463-467



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