HIV This Week

Zar HJ, Madhi SA. Pneumococcal conjugate vaccine—a health priority. S Afr Med J 2008; 98(6):463-7.

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 is a highly effective intervention to reduce invasive pneumococcal disease and pneumonia. Studies evaluating a 9-valent pneumococcal conjugate vaccine in South Africa and The Gambia reported a 72 – 77% reduction in vaccine-serotype-specific invasive disease in vaccinated children. As many of the pneumococcal serotypes associated with antibiotic resistance are included in pneumococcal conjugate vaccine, vaccination has also been associated with a reduction in antimicrobial-resistant invasive disease. Pneumococcal conjugate vaccine may also reduce childhood mortality, especially in places with limited access to health care, as shown in Gambian study in which pneumococcal conjugate vaccine reduced childhood mortality by 16%. In addition to the direct effects of pneumococcal conjugate vaccine, there is a substantial reduction in disease burden through indirect protection of non-vaccinated populations. Pneumococcal conjugate vaccine is immunogenic in HIV-infected children and provides protection against invasive disease or pneumonia in a substantial number of children. Although the efficacy of pneumococcal conjugate vaccine 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 HIV-uninfected children, while the reduction in pneumonia in HIV-infected children is 15 times greater. However, the long-term efficacy of pneumococcal conjugate vaccine wanes in HIV-infected 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, pneumococcal conjugate vaccine is much less accessible to children in developing countries due to cost and availability. Cost-effectiveness analysis indicates that use of pneumococcal conjugate vaccine is potentially highly cost-effective, at tiered pricing, even in very low-income countries. Widespread availability and vaccination with pneumococcal conjugate vaccine is urgently needed for all children under 2 years of age in South Africa. In addition, the use of pneumococcal conjugate vaccine for all HIV-infected children under 9 years should be prioritised.

Editors’ note: WHO recommends that countries with high HIV prevalence prioritise the introduction of pneumococcal conjugate vaccine. Infants and children living with HIV are protected directly by the vaccine and indirectly by the reduced transmission of pneumococci that results from a universal immunisation programme.