A new study by the U.S. Centers for Disease Control and Prevention (CDC) found that most of the victims of a 2006 mumps outbreak had already received the recommended vaccination against the virus, raising concerns about whether or not a booster shot or a new vaccine may be required to fully protect people from the mumps.
The 2006 outbreak was the country’s biggest since shortly before children began receiving a second booster shot in 1990. The outbreak affected 6,600 people, most of whom were college students ages 18-24 in Illinois, Iowa, Kansas, Minnesota, Missouri, Nebraska, South Dakota and Wisconsin. Of those aware of their vaccination status, 84 percent had received the recommended two mumps shots, the study found.
Public health officials were stunned to learn of the “two-dose vaccine failure”, and that the vaccines’ immunity had waned so soon.
Although the virus involved in the 2006 outbreak was a relatively new strain not targeted by the vaccine, evidence from outbreaks elsewhere has shown the shots are effective against the new strain.
In a report about the study, the researchers wrote the virus likely came from the United Kingdom, where a much larger mumps outbreak of the same strain occurred and where mumps shots are voluntary. Indeed, many cases are brought from overseas as numerous 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,” researcher Dr. Jane Seward, deputy director of the CDC’s viral diseases division, told the Associated Press.
Mumps, which causes fever and swollen salivary glands in the cheeks, is spread among people in close contact via respiratory secretions and saliva. College students are particularly susceptible, with sharing drinks and utensils and sexual activity likely increasing their exposure.
Prior to the vaccine there were about 2 million cases of mumps in the U.S. each year, which included complications such as viral meningitis, deafness and testicle inflammation, which can cause sterility.
Merck & Co. makes the only U.S. vaccine, which hasn’t been changed since 1967 when it was first introduced. Barbara Kuter, Merck’s executive director of pediatric affairs, said there are no plans to change the vaccine. It was put in the combination measles-mumps-rubella shot during the 1970s, and over 500 million doses have been sold since then.
The American Academy of Pediatrics (AAP) is in discussions with the CDC about possible changes to the recommended vaccine schedule, according to Dr. John Bradley, a member of the AAP’s committee on infectious diseases. Current recommendations call for two shots, one at 12 to 15 months and the other at age 4 to 6.
Dr. Stephen Marcella, an epidemiologist at University of Medicine and Dentistry of New Jersey’s School of Public Health, told the AP that giving everyone a third shot might not be cost effective, but should be considered for college students.
Some, including Dr. William Schaffner, head of preventive medicine at Vanderbilt University School of Medicine, say what’s need is a longer-lasting shot.
“It’s clear that over time, immunity wanes somewhat,” he told the AP. “We need a better vaccine.”
Seward said previous CDC studies on the 2006 outbreak found two mumps shots protected about 85 percent of people from the new strain, not enough not to prevent spread even with the nearly 90 percent vaccination rate at that time.
On the Net:
A report about the study was published in Thursday’s New England Journal of Medicine. A summary can be viewed at http://content.nejm.org/cgi/content/abstract/358/15/1580.