Serum levels of measles IgG antibody activity in children under 5 years in Dar-es-Salaam, Tanzania.

Measles IgG antibody levels were estimated in sera from 685 Tanzanian children, 374 (54.6%) boys and 311 (45.4%) girls aged 18 months to 5 years, using an enzyme-linked immunosorbent assay (ELISA). The children were screened for HIV-1 and 2 antibodies using ELISA, and reactive sera were confirmed by Western blot. Nutritional status was assessed by anthropometry. Overall measles vaccination coverage was 98.8%. Measles antibody activity was not detected in 41 (6.0%) children, and ten (1.5%) had antibody levels below 200 mIU/ml, the cut-off level considered to be protective. The non-reactive samples were from one unvaccinated child, one child with unknown vaccination status and 39 vaccinated children. Measles IgG antibody levels were higher in girls (3452.1 mIU/ml) than in boys (2928.2 mIU/ml) (p = 0.02). Higher mean levels were found in children with a history of low birthweight (< 2.5 kg) (p = 0.03). There were no significant differences in measles antibody levels with regard to variations in nutritional status. No correlation (r2 = 0.002) was found between antibody levels and time elapsed since vaccination. In a multivariable logistic regression analysis, children who were HIV-seropositive (n = 9) were more likely to have non-protective antibody levels < 200 mIU/ml (OR = 5.85; 95% CI: 1.37-24.93).