The epidemiology of pneumococcal infection in children in the developing world

Pneumonia causes about three million deaths a year in young children, nearl y all of which are in developing countries. Streptococcus pneumoniae (the p neumococcus) is the most important bacterial cause of pneumonia in young ch ildren and so is likely to be responsible for a high proportion of these de aths. The pneumococcus is also responsible for a substantial proportion of the 100 000-500 000 deaths that occur from meningitis in children each year . The incidence of invasive pneumococcal disease in children in the develop ing world is several times higher than in industrialized countries. This di screpancy may, in part, be due to socio-economic differences but genetic fa ctors may also play a role. Children with sickle cell disease have a substa ntially increased risk of invasive pneumococcal infection and a search is b eing made for other possible genetic risk factor!;. Infection with human im munodeficiency virus (HIV) also predisposes to invasive pneumococcal diseas e and so the incidence of this disease in young children is expected to ris e as increasing numbers of African and Asian children are born with a perin atally acquired HIV infection. Until recently, pneumococcal infections coul d be treated effectively with penicillin, a cheap and safe antibiotic. Howe ver, pneumococci that are resistant to penicillin are becoming prevalent in many countries, necessitating a change to more costly antibiotics which ma y be beyond the reach of the health services of poor, developing counties. The spread of antibiotic resistance has provided an added stimulus to the d evelopment of vaccines that might be able to prevent pneumococcal disease i n infants. Recently developed polysaccharide-protein conjugate vaccines sho w promise and are now undergoing field trials. How deployment of these vacc ines will influence the balance between invasive pneumococcal infections an d asymptomatic nasopharyngeal carriage of pneumococci is uncertain.