| Epidemiological
backgroundPneumococcal
vaccine development initiative
Prevention of disease by vaccination is one of the
approaches to control the high rates of morbidity and mortality due to this organism. A
polyvalent polysaccharide vaccine has been available for several years but this vaccine is
poorly immunogenic in infants and young children, who are at highest risk for invasive
disease, and does not result in immunological memory. A 7-valent glycoprotein conjugate
vaccine has recently been licensed for use in children in the United States. Several new
9- or 11-valent conjugate vaccines are undergoing trials. Other candidate vaccines using
protein antigens that are common to all pneumococci, are also in different phases of
testing. These vaccines, if efficacious, are likely to have an important role in reducing
childhood mortality in developing countries. The WHO has an important role in promoting
research to evaluate and planning strategies for introduction of these vaccines in
developing country populations.
Current status of activities in pneumococcal vaccine
development
The status of pneumococcal vaccines and the research and
development needs were discussed and prioritized in a meeting in WHO in 1998 and updated
in a meeting jointly organised by WHO and the GAVI Task Force on Research and Development
in April 2001. These research priorities have been combined with other priority activities
required for vaccine introduction and is being formulated into an Accelerated Development
and Introduction Plan (ADIP). The plan targets at initiating the introduction of
pneumococcal conjugate vaccines in Vaccine Fund eligible countries in 2006-7.
Meanwhile research to establish the value of pneumococcal
vaccines are in progress. Studies are being initiated to measure the burden of pneumonia
and pneumococcal disease in developing countries. Efficacy trials with 9 or 11-valent
pneumococcal conjugate vaccines are in progress in South Africa, The Gambia and The
Philippines. The South Africa trial is just completed and results are expected in May
2002. The other two trials are expected to be completed in 2005. Trials evaluating the
safety and immunogenicity of maternal immunization, neonatal immunization and immunization
of HIV-infected children are also ongoing.
A Radiology Working Group of Pneumococcal Vaccine
Trialists, convened by WHO, has developed a standardised method to measure radiological
pneumonia, which may be used to measure pneumonia burden and evaluate the impact of
vaccination. A training and self-ssessment software has been developed for this purpose.
Other standardization efforts include the development of standard procedures to study
nasopharyngeal carriage of pneumococcus following vaccination and for estimating
cost-effectiveness of pneumococcal vaccination.
(Posted June 2002)
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