Immune response to measles vaccine in 6 month old infants in Papua New Guinea.

Summary objective To assess the efficacy of the current measles immunization schedule in Papua New Guinea,which is to give the first dose at 6 months of age and the second at 9 months.methods Humoral immune response study of 140 Papua New Guinean infants at 6 months of age,measuring measles IgG antibodies by enzyme immunoassay before and 85 days after the 6-month doseof measles vaccine.results After vaccination at 6 months, 35.7% of infants developed a level of measles antibodiesconsistent with protection (IgG >330 IU⁄ml); 17.7% had an antibody response (150–330 IU⁄ml) that islikely to afford some protection; 46.8% had no detectable antibody response (IgG 95% if the first dose is given at 12or 15 months, and >99% after the second dose. PNG has adifferent epidemiology of measles to industrialized coun-tries, where measles affects children older than 1 year andthe disease is generally mild. In PNG measles has a highattack rate and high mortality in infants (Mgone et al.2000). Although the 6 month dose of measles vaccine inPNG was introduced to protect infants younger than9 months, there has been uncertainty about the efficacyand effectiveness of such an approach. A small study in thelate 1980s using standard titre measles vaccine in infantsaged 6–7 months in the Southern Highlands of PNG