Measles reimmunization in children seronegative after initial immunization.

OBJECTIVE

To evaluate the success of measles reimmunization in children without measles antibody after the initial dose of measles vaccine.

DESIGN AND SETTING

A prospective clinical trial in Olmsted County, Minnesota, and Northern Newfoundland and Labrador in Canada.

SUBJECTS

A total of 130 healthy white, Innu, and Inuit schoolchildren. All subjects had received the post-1980 Moraten measles vaccine 4 to 11 years earlier.

METHODS

Children previously identified as measles antibody seronegative or equivocal after 1 dose of measles vaccine were entered into the trial and reimmunized. Measles antibody was measured a minimum of 6 weeks later using a whole-virus IgG measles-specific enzyme-linked immunoassay (EIA).

RESULTS

Of the 130 children reimmunized, 106 (81.5%) became measles antibody seropositive, but 24 children (18.5%) remained seronegative. Younger age at initial immunization (<13 months vs > or = 13 months) was significantly associated with 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 seropositive for measles antibody, despite the fact that almost 20% of children did not have measurable antibodies 4 to 11 years following a first dose. These findings suggest that the current public health policy recommending a 2-dose measles immunization strategy, with the second dose given at school entry, will provide high levels of immunity in the community.