Low IgG Seroconversion among Persons Vaccinated against Measles, Republic of Congo

We report a low (38.7%; p<0.0001) level of IgG seroconversion in patients who were positive for measles virus IgM in the Republic of Congo, despite a history of vaccination. Considering this country's recurring measles epidemics, more effective immunization strategies, including vaccine delivery methods, are needed to prevent measles outbreaks.