What can children gain from pneumococcal conjugate vaccines?

In excess of 1 million young children die every year as a consequence of disease caused by Streptococcus pneumoniae, the vast majority in developing countries. Although the first vaccine against the Pneumococcus was produced before the First World War, licensure of the first vaccine with documented efficacy against severe infections in infants and young children did not occur until February 2000 in the United States. This conjugate vaccine consists of purified polysaccharide, from each of seven pneumococcal serotypes, chemically linked to a carrier protein. A high degree of efficacy of the new vaccine against potentially life-threatening infections has been shown in both poor and affluent countries. The vaccine's potential to protect from acute otitis media, however, is very limited, although encouraging indirect effects, such as reduced antibiotic prescriptions, have been reported. An inherent problem with the new pneumococcal conjugate vaccines is that, while more than 20 pneumococcal serotypes may cause invasive disease, only a more limited number of polysaccharides, 11 or so, can in practice be conjugated to carrier protein as part of a single vaccine formulation. Because of variation in the ranking of serotypes most commonly responsible for pneumococcal disease, by region, age and disease manifestation, compromise was required in selecting serotype-specific saccharides for inclusion. Conclusion: Complex conjugate technology comes at a price, and the present costs keep most of the world's children far out of reach of an effective vaccine. However, the pneumococcal conjugate vaccine is a highly functional weapon against deadly pneumococcal infections, and strenuous efforts are needed to maximise its accessibility to children most at risk.