Two Dose MMR Fails: Largest Outbreak of Mumps in the United States in 2006
Posted by vaccinesme on Monday, January, 26 2009 and filed under MMR
Key topics: Mumps Vaccine Failure MMR

Gustavo H. Dayan, M.D., M. Patricia Quinlisk, M.D., M.P.H., Amy A. Parker, M.S.N., M.P.H., Albert E. Barskey, M.P.H., Meghan L. Harris, M.P.H., Jennifer M. Hill Schwartz, M.P.H., Kae Hunt, B.A., Carol G. Finley, B.S., Dennis P. Leschinsky, B.S., Anne L. O'Keefe, M.D., M.P.H., Joshua Clayton, B.S., Lon K. Kightlinger, pH.D., M.S.P.H., Eden G. Dietle, B.S., Jeffrey Berg, Cynthia L. Kenyon, M.P.H., Susan T. Goldstein, M.D., Shannon K. Stokley, M.P.H., Susan B. Redd, Paul A. Rota, pH.D., Jennifer Rota, M.P.H., Daoling Bi, M.S., Sandra W. Roush, M.T., M.P.H., Carolyn B. Bridges, M.D., Tammy A. Santibanez, pH.D., Umesh Parashar, M.B., B.S., M.P.H., William J. Bellini, pH.D., and Jane F. Seward, M.B., B.S., M.P.H. Recent Resurgence of mumps in the United States. NEJM Volume 358:1580-1589, April 10, 2008, Number 15.


Background The widespread use of a second dose of mumps vaccine among U.S. schoolchildren beginning in 1990 was followed by historically low reports of mumps cases. A 2010 elimination goal was established, but in 2006 the largest mumps outbreak in two decades occurred in the United States.

Methods We examined national data on mumps cases reported during 2006, detailed case data from the most highly affected states, and vaccination-coverage data from three nationwide surveys.

Results A total of 6584 cases of mumps were reported in 2006, with 76% occurring between March and May. There were 85 hospitalizations, but no deaths were reported; 85% of patients lived in eight contiguous midwestern states. The national incidence of mumps was 2.2 per 100,000, with the highest incidence among persons 18 to 24 years of age (an incidence 3.7 times that of all other age groups combined). In a subgroup analysis, 83% of these patients reported current college attendance. Among patients in eight highly affected states with known vaccination status, 63% overall and 84% between the ages of 18 and 24 years had received two doses of mumps vaccine. For the 12 years preceding the outbreak, national coverage of one-dose mumps vaccination among preschoolers was 89% or more nationwide and 86% or more in highly affected states. In 2006, the national two-dose coverage among adolescents was 87%, the highest in U.S. history.

Conclusions Despite a high coverage rate with two doses of mumps-containing vaccine, a large mumps outbreak occurred, characterized by two-dose vaccine failure, particularly among midwestern college-age adults who probably received the second dose as schoolchildren. A more effective mumps vaccine or changes in vaccine policy may be needed to avert future outbreaks and achieve the elimination of mumps.

The researchers make a speculation that the "wrong" type of mumps was vaccinated against. Looks like a third-dose of MMR is going to be called for with the "right" type of mumps. In 2006 national two-dose coverage was 87% amongst adolescents - is that enough for "Herd Immunity"?

Just like with measles, mumps is mild disease in childhood, in fact, even milder but it is now appearing in older age groups due to vaccination policies. In older age groups there is increased risk of orchitis (inflammation, swelling and infection of the testicles).