Effect of early immunization on antibody response to reimmunization with measles vaccine as demonstrated by enzyme-linked immunosorbent assay (ELISA)

A measles epidemic in San Antonio, Texas provided a population of children who were immunized at ≤10 months of age and reimmunized at ≥15 months of age. Of these children, 302 were evaluated for measles antibody by the sensitive enzyme-linked immunosorbent assay (ELISA), and their responses were compared with those of 300 children who had been immunized at the customary time (≥15 months) with a single immunization. There were only five seronegative findings in each group. The children immunized at the customary time did have significantly higher (P < .001) antibody titers than the children immunized at ≤10 months and reimmunized at ≥15 months. These results indicate that early immunization followed by reimmunization may be indicated when young infants are at significant risk of measles exposure. This approach should not create an increased number of serologically nonresponsive children when reimmunized at ≥15 months.