Five Cases of Measles Secondary Vaccine Failure with Confirmed Seroconversion after Live Measles Vaccination

We report 5 patients with secondary vaccine failure (SVF) who were infected with natural measles 2, 5, 5, 7 and 12 years, respectively, after vaccination with further attenuated live measles vaccine during infancy. Their seroconversion had been confirmed after vaccination. Three of the 5 patients had mild (modified) measles, while the remaining 2 patients had typical measles. The hemagglutination inhibition antibody titers to measles virus in paired acute and convalescent sera showed a secondary response pattern in 4/5 patients, and a primary response pattern was present in the remaining patient. Measles IgM antibodies were present in all patients during the convalescent stage. The patient with the primary response pattern may have had a decrease in the B cell memory during the 5-year period between vaccination and infection. This may be the first SVF case report that confirms the existence of completely waning immunity in recipients of the further attenuated live measles vaccines.