ELISA underestimates measles antibody seroprevalence in US military recruits.

The prevalence of antibodies to measles, mumps, and rubella in US military recruits is of importance to public health leaders. We performed ELISA testing using a commercially available product on samples from 537 recruits obtained in 1998, of which 437 were positive (81%). We then performed a validation study in a subsample of the population using plaque reduction neutralization (PRN) to assess misclassification error. This resulted in a corrected estimate of the prevalence of immunity to measles of 96% (95% CI: 92-100%). The military vaccinates a percentage of recruits who are likely to be immune if more sensitive testing, such as PRN, was used.