MEASLES REIMMUNIZATION IN CHILDREN SERONEGATIVE AFTER INITIAL IMMUNIZATION

Objective.-To evaluate the success of measles reimmunization in childr en without measles antibody after the initial dose of measles vaccine. Design and Setting.-A prospective clinical trial in Olmsted County, M innesota, and Northern Newfoundland and Labrador in Canada. Subjects.- A total of 130 healthy white, Innu, and Inuit schoolchildren. All subj ects had received the post-1980 Moraten measles vaccine 4 to 11 years earlier. Methods.-Children previously identified as measles antibody s eronegative or equivocal after 1 dose of measles vaccine were entered into the trial and reimmunized. Measles antibody was measured a minimu m of 6 weeks later using a whole-virus IgG measles-specific enzyme-lin ked immunoassay (EIA). Results.-Of the 130 children reimmunized, 106 ( 81.5%) became measles antibody seropositive, but 24 children (18.5%) r emained seronegative. Younger age at initial immunization (<13 months vs greater than or equal to 13 months) was significantly associated wi th lack of seropositive antibody levels following reimmunization (odds ratio, 3.9; 95% confidence interval, 1.5-9.7). In addition, antibody levels after reimmunization were significantly reduced with increasing time since initial immunization (P=.001). Conclusions.-After 2 doses of measles vaccine, 98.2% of all subjects in this study were seroposit ive for measles antibody, despite the fact that almost 20% of children did not have measurable antibodies 4 to 11 years following a first do se, These findings suggest that the current public health policy recom mending a 2-dose measles immunization strategy, with the second dose g iven at school entry, will provide high levels of immunity in the comm unity.