Simple method for differentiating measles vaccine from wild-type strains using loop-mediated isothermal amplification.

Because of increasing measles vaccine coverage, the proportion of patients with modified measles has been increasing. Such patients have low-grade fever with very mild eruptions similar to vaccine-related adverse events. Differentiation between these two pathogenic conditions is required to improve the quality of laboratory-based measles surveillance. In this study, vaccine-specific and wild-type specific primer sets were designed for loop-mediated isothermal amplification in the N gene, and vaccine strains, C1, D3, D4, D5, D8, D9, G3 and H1 wild strains were examined. Three vaccine strains were efficiently amplified using a vaccine-specific primer set with an approximately 10-times higher sensitivity than wild-type primer. Modified measles was differentiated from vaccine-associated cases by this system, but limitations were encountered with the other genotypes.