AN EVALUATION OF MEASLES REVACCINATION AMONG SCHOOL-ENTRY-AGED CHILDREN

Background. A two dose measles vaccination schedule is recommended rou tinely for all school-entry-aged children. We evaluated this recommend ation by determining both measles antibody seroprevalence and the resp onse to revaccination in seronegative children in this age group. Meth ods. Children 4 to 6 years of age who had received a single dose of me asles vaccine between the ages of 15 to 17 months were tested for meas les antibody by using an enzyme-linked immunosorbent assay (ELISA) mic roneutralization technique. Seronegative children were revaccinated an d again tested for measles antibody (immunoglobulin M [IgM] and neutra lizing). Results. Of 679 children tested, 37 (5.4%) were seronegative. Seronegativity was not significantly associated with age, sex, race, age at initial vaccination, time since vaccination, or maternal year o f birth. However, children of mothers with a college degree were 12 ti mes more likely to be seronegative than children of mothers whenever a ttended college (P < .01). Of the 37 seronegative children, 36 serocon verted after revaccination-33 producing IgM measles antibody, suggesti ve of a primary immune response. The cost per seroconversion would hav e been an estimated $415 if all 679 children had been revaccinated. Co nclusions. Revaccination reduces the pool of children who are suscepti ble to measles. Although the cost per seroconversion is high, a two-do se schedule should reduce the substantial costs of controlling measles outbreaks by reducing the number of outbreaks.