Measles immunity after revaccination: results in children vaccinated before 10 months of age.

Measles immunity was studied in children in a private pediatric practice who had been revaccinated because they had received their primary measles vaccination before 1 year of age. Antibody was measured in 72 of these children who had received the first injection of live measles virus vaccine at less than 10 months of age, and the second at greater than 1 year of age. Of the 72 children, 29 (40%) had no detectable antibody and the geometric mean titer for the group was approximately 1:4. Of the children with low antibody titers, 15 were given a third injection of measles vaccine and five (33%) still did not respond. Cell-mediated immunity as indicated by lymphocyte transformation to measles antigen was measured in 11 of the children. Five (45%) had responses to measles antigen, but the responses did not correlate with the presence or absence of antibody. This study confirms the observation that revaccination is unsuccessful in many children who received measles vaccine in the first year of life, and shows that even a third injection of vaccine may fail to produce a significant antibody response.