IMMUNOGLOBULIN-G ANTIBODY-RESPONSES TO POLYVALENT PNEUMOCOCCAL VACCINE IN CHILDREN IN THE HIGHLANDS OF PAPUA-NEW-GUINEA

The immunoglobulin G (IgG) antibody responses to a pneumococcal polysa ccharide vaccine were examined for 480 children aged 3 months to 5 yea rs and living in Tari, Southern Highlands Province, Papua New Guinea, Antipneumococcal IgG to the seven serotypes most frequently causing in vasive disease (types 2, 5, 6B, 7F, 14, 19F, and 23F) was measured by an enzyme-linked immunosorbent assay in serum collected before vaccina tion and 1 and 6 months after vaccination. Prevaccination antibody lev els fell rapidly after 3 months of age and remained low throughout the first 2 Sears of life. One month after vaccination, geometric mean ti ters of antipneumococcal IgG to serotypes 2, 7F, 23F, and 5 were at le ast twice those of antibodies in nonvaccinated children of the same ag e from the ages of 5, 6, 9, and 12 months onwards, respectively; postv accination antibody responses to serotypes 6B, 14, and 19F rose gradua lly during the second year of life. Elevated antibody titers to seroty pes 2 and 7F were maintained 6 months after vaccination. Thus, young P apua New Guinean children are capable of mounting a good immune respon se to some pneumococcal capsular polysaccharides from a young age, and the antibody responses to capsular polysaccharides are consistent wit h studies in developed countries. However, in Papua New Guinea, the se rogroup distribution of invasive disease matches the immunogenic compo nents of the pneumococcal polysaccharide vaccine more closely than in developed countries, a fact which helps to explain the results of cont rolled trials in Papua New Guinea, in which this vaccine prevented dea th and severe morbidity from pneumonia in young children.