Mumps Vaccine Good, Not Perfect
2006 Mumps Outbreak Biggest in 20 Years Despite Vaccination
Might the Canada outbreaks spread to the U.S.? Seward says there's no sign this is yet happening.
"Maine has had some cases this year, and we looked carefully for connections with Canada but have not noticed any -- nothing that has become established here," she says. "We expect we are probably bombarded with mumps from all over the world a lot of the time, because a lot of the world doesn't use mumps vaccine. Our surveillance isn't good enough to detect every mumps case that comes in, but we did detect some transport in 2006 from the U.K."
The U.K. epidemic in 2004 and 2005 was blamed on the relatively high number of people who refused to vaccinate their children with the measles-mumps-rubella (MMR) vaccine. The U.K. epidemic involved over 10,000 cases of mumps -- an infection rate 50 times higher than that seen in the U.S. during the 2006 outbreak, Seward says.
The two-dose vaccine seemed so effective that the U.S. set a goal of eliminating mumps by 2010. The current outbreak has upset that plan.
"This outbreak was unexpected. We were down to very, very low levels of mumps in the country, and we are still trying to understand why it occurred," Seward says. "The problem is some waning of immunity after two doses, but we right now we are just watching the epidemiology very carefully to consider policy changes that might be needed."
Would the CDC consider recommending a routine third dose of mumps vaccine?
"We see no need for a routine third dose. The cost benefit would not be there," Seward says. "But if we see again some outbreaks starting and continuing, we would at that point start a third dose in an outbreak setting to see if it limited the outbreak. But it would have to be a large outbreak on a lot of college campuses to show a benefit."
Seward and colleagues report their findings in the April 10 issue of The New England Journal of Medicine.