EPIDEMIOLOGY OF INVASIVE PNEUMOCOCCAL DISEASE IN THE WESTERN REGION, THE GAMBIA

Background. Streptococcus pneumoniae is a major cause of morbidity and mortality in young children in the developing world, The recent devel opment of pneumococcal polysaccharide/protein conjugate vaccines may m ake possible prevention of this infection, However, little is known ab out the epidemiology of invasive pneumococcal disease in children in t he developing world, Objectives, To determine the incidence and epidem iologic features of invasive pneumococcal disease in children resident in a semiurban area of The Gambia. Method, The study was part of a la rge trial of an Haemophilus influenzae type b vaccine that recruited 4 2 848 children at the age of 2 months during the period March, 1993, t o October, 1995, Follow-up of study children continued until December 31, 1995; therefore the first children to enter the trial were followe d for 2.5 years and the last for just a few months. During the period of surveillance, 2256 children were investigated for possible invasive pneumococcal disease when they presented to a hospital or health cent er, Results, We detected 110 cases of pneumococcal disease. Pneumonia was the most common form of invasive pneumococcal disease observed (75 .5% of patients), The incidence of pneumococcal disease was 224 [95% c onfidence interval (CI) 171, 277] per 100 000 child years among childr en ages 2 to 11 months, 139 (95% CI 93, 184) per 100 000 among childre n ages 12 to 23 months and 82 (95% CI 21, 143) per 100,000 among child ren ages 24 to 35 months. Pneumococci of serogroups 14, 6, 5, 23, 19, 46 and 2 were isolated most frequently, Susceptibility to pneumococcal disease was not increased significantly among Haemophilus influenzae type b-vaccinated children, Conclusions, The pneumococcus is a major c ause of bacterial infection in The Gambia, A proposed nine-valent pneu mococcal conjugate vaccine for developing countries containing conjuga tes of serogroups 1, 4, 5, 6, 9, 14, 18, 19 and 23 would cover 74%% of cases of invasive pneumococcal disease in children resident in the We stern Region of The Gambia.