Mumps Epidemic in Iowa (2006)

In March 2006, Iowa experienced a major outbreak of mumps, marking the largest epidemic of the disease in the United States since 1988, with a total of 219 reported cases. The average age of those infected was 21 years. Among the 133 individuals whose vaccination histories were examined, 87 (65%) had received two doses, 19 (14%) had received one dose, 8 (6%) had received none, and 19 (14%) had undocumented status. This data indicated that at least 79% of those infected had received one or more doses, raising concerns about the effectiveness of the mumps immunization in preventing outbreaks, especially among young adults presumed to be protected.