Immune modulation after measles vaccination of 6-9 months old Bangladeshi infants

Measles still causes high mortality in children younger than 1 year of age. Administration of high titre measles vaccines before 7 months of age led t o increased overall mortality, raising questions as to the immunological ef fects of measles vaccine in young infants. We investigated the immune respo nse to standard titre vaccines given to children in Bangladesh in a single dose at age 9 months, or two doses at 6 and 9 months. Of the children vacci nated at age 9 months, 95% serocoverted, compared with 70% at age 6 months. Delayed-type-hypersensitivity reactions to candida antigen were significan tly reduced in both vaccine groups at 6 weeks post-vaccination, but respons es to other recall antigens studied were not significantly different from c ontrols. In both vaccine groups, peripheral blood lymphocytes isolated at 6 and 24 weeks after vaccination showed significantly higher expression of a ctivation markers upon in vitro stimulation, and a sustained increase in IL -2 production. These findings suggest prolonged immune activation after mea sles vaccination at the same time as some reduction in delayed hypersensiti vity responses. Further study of the clinical effects of these changes is w arranted. (C) 2001 Elsevier Science Ltd. All rights reserved.