Immunologic 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 study, immunologic parameters in 64 Peruvian children who had been immunized an average of 27 months earlier with high-titer vaccines were compared with parameters in 76 recipients of low-titer vaccines. Delayed-type hypersensitivity, lymphocyte phenotype distributions by flow cytometry, and lymphoproliferation after phytohemagglutinin (PHA) stimulation were assessed. High-titer recipients had smaller indurations to tetanus, diphtheria, and Proteus (P < .05) antigens, decreased PHA stimulation (P = .04), and a lower percentage of CD4⁺ lymphocytes (P = .04) than low-titer recipients. After adjustment for sex, concurrent illnesses, and other variables in regression analyses, high-titer recipients had a lower percentage of CD4⁺ lymphocytes (P = .025) and decreased lymphocyte 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.