Mumps outbreak in vaccinated children, teens

An ongoing mumps outbreak has sickened 1,521 people in New York and New Jersey. "Patient Zero" was an 11-year-old boy who got infected with mumps during a summer visit to Great Britain. He came down with symptoms while at a summer camp for Orthodox Jewish boys; campers and staff then carried the disease back to their communities. Nineteen people have been hospitalized; no one has died. Scores of people have developed complications, including 55 cases of swollen testicles, five cases of pancreatitis, two cases of meningitis, one case of temporary deafness, one case of Bell's palsy, and one case of inflamed ovaries.

The infections happened despite high coverage with the measles-mumps-rubella (MMR) vaccine. Among patients ages 7 to 18 -- the age group that had the most cases -- 85% of patients had received the two recommended MMR vaccine doses.

This doesn't mean the MMR vaccine isn't working, says epidemiologist Kathleen Gallagher, DSc, MPH, the CDC's team leader for measles, mumps, and rubella. "Two doses of mumps vaccine is believed to be 90% to 95% effective," Gallagher says. "But that means people can still get mumps. If the vaccine is 90% effective and 100 people are exposed to mumps, 10 will get the disease."

Because of continued spread, health authorities working with communities in Orange County are giving schoolchildren a third dose of the MMR vaccine. Gallagher says it will be two or three months before it's known whether the effort succeeded. A report on the mumps outbreak appears in the Feb. 12 issue of the CDC's Morbidity and Mortality Weekly Report.