Detection of measles vaccine virus and measles-specific immunoglobulin M in children vaccinated against measles-mumps-rubella during measles outbreak

Information regarding the detection perioid of measles vaccine virus (MeVV) RNA in human nasopharyngeal samples and measles-specific antibodies following measles-mumps-rubella (MMR) vaccination is limited. During contact tracing for a measles outbreak at a hospital in Republic of Korea, 4 out of 206 children vaccinated with MMR underwent real-time RT-PCR assay for measles and measles-specific antibodies test. Measles virus RNA was detected in 2 children, all of which was vaccine virus strain RNA (genotype A). In a healthy 27-month-old boy, MeVV RNA was detected 448 days after MMR vaccination. Measles-specific IgM was positive 1097 days following vaccination in a 4-year-old girl. MeVV RNA and measles-specific IgM were detected for a considerable period following primary MMR vaccination. Physicians should exercise caution when interpreting positive RT-PCR results for MeVV or measles-specific IgM from a child with measles-associated symptoms who has been recently vaccinated against measles.