IMMUNOLOGICAL PARAMETERS 2 YEARS AFTER HIGH-TITER MEASLES IMMUNIZATION IN PERUVIAN CHILDREN

Immunization with high-titer measles vaccines has been associated with excess mortality in children 2-4 years after vaccination. In this stu dy, immunologic parameters in 64 Peruvian children who had been immuni zed an average of 27 months earlier with high-titer vaccines were comp ared with parameters in 76 recipients of low-titer vaccines. Delayed-t ype hypersensitivity, lymphocyte phenotype distributions by flow cytom etry, and lymphoproliferation after phytohemagglutinin (PHA) stimulati on were assessed. High-titer recipients had smaller indurations to tet anus, diphtheria, and Proteus (P < .05) antigens, decreased PHA stimul ation (P = .04), and a lower percentage of CD4+ lymphocytes (P = .04) than low-titer recipients. After adjustment for sex, concurrent illnes ses, and other variables in regression analyses, high-titer recipients had a lower percentage of CD4+ lymphocytes (P = .025) and decreased l ymphocyte proliferation to PHA (P = .058). These results may provide a clue to the pathogenesis of delayed excess mortality after high-titer measles vaccination in some developing countries.