Outbreak reveals weakness in mumps vaccine, study says
Another dose or new shot might be considered
TRENTON, N.J. - Most of the college students who got the mumps in an outbreak in 2006 had received the recommended two vaccine shots, according to a study that raises questions about whether a new vaccine or another booster shot is needed.
The outbreak was the biggest in the United States since states began requiring a second shot for youngsters in 1990.
Nearly 6,600 people became sick with the mumps, mostly in eight Midwest states, and the hardest-hit group was college students ages 18 to 24. Of those in that group who knew whether they had been vaccinated, 84 percent had had two mumps shots, according to the study by the Centers for Disease Control and Prevention and state health departments.
That "two-dose vaccine failure" startled public health analysts, who had not expected immunity to wane so soon - if at all.
The mumps virus involved was a relatively new strain, not the one targeted by the vaccine, although there's evidence from outbreaks elsewhere that the shots work well against the new strain.
The researchers, reporting in the New England Journal of Medicine, note that the virus probably came from travelers or students from the United Kingdom, where mumps shots are voluntary and there was a much larger outbreak of the same strain. Many countries don't vaccinate against mumps.
"If there's another outbreak, we would evaluate the potential benefit of a third dose to control the outbreak," said Jane Seward, deputy director of the CDC's viral diseases division.
Mumps is spread by respiratory secretions and saliva among people in close contact, making college students particularly susceptible. Students' sharing of drinks and utensils, and sexual activity, probably increased their exposure.
Mumps causes fever and swollen salivary glands in the cheeks. Before the vaccine, complications such as deafness, viral meningitis, and testicle inflammation, which can cause sterility, were common and there were a couple million cases a year in the nation.
The only US vaccine, made by
About 500 million doses have been sold since the 1970s, when it was put in the combination measles-mumps-rubella shot.
Dr. John Bradley, a member of the American Academy of Pediatrics committee on infectious diseases, said his group is talking about possible changes to the recommended schedule for the vaccine with CDC and other health agencies.
Now two shots are recommended, one at 12 to 15 months and the other at age 4 to 6.
It might not be cost effective to give everyone a third shot, but it should be considered for college students, said Dr. Stephen Marcella, an epidemiologist at University of Medicine and Dentistry of New Jersey's School of Public Health.
Dr. William Schaffner, head of preventive medicine at Vanderbilt University School of Medicine, said what's need is a longer-lasting shot. "It's clear that over time, immunity wanes somewhat," he said. "We need a better vaccine."