The 2006 mumps outbreak in the US has affected also those who got the second booster shot, introduced in 1990. This came as a surprise for many experts, as it was widely believed that the second shot would boost immunity to a high level and for a longer period of time.
The virus is spread by coughing and sneezing and it was nearly eradicated in the U.S. after Merck & Co. released its MumpsVax vaccine in 1967. The current infection rate is about 2.2 people of every 100,000.
MUMPS: The virus, which causes fever and inflamed salivary glands under the jaw and in the cheeks, primarily infected college students in the Midwest who had received the vaccine as children. It was the first time the virus spread among people who followed the recommended two-shot vaccination regimen, showing protection may decline with time, the CDC said.
Questions linger about the Mumps Booster Vaccine
In the 2006 outbreak, nearly 7,000 got the mumps, most of them in the Midwest and mostly college students ages 18 to 24. Of the people in that group who knew whether they had been vaccinated or not, 84 percent had had two mumps shots, according to the study by the Centers for Disease Control and Prevention and state health departments.
“If there’s another outbreak, we would evaluate the potential benefit of a third dose to control the outbreak,” said researcher Dr. Jane Seward, deputy director of the CDC’s viral diseases division.
It appears that after two doses the vaccine is 80 percent to 90 percent effective, which means that the rest of 10 to 20 percent will get infected but their disease will most likely be less severe. Mumps or epidemic parotitis is usually detected by a painful swelling of the salivary glands. In males, painful testicular swelling may be also present.
“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.”
Mychiro Source: N Engl J Med Volume 358: pp 1580-1589, April 10, 2008, Number 15. – Mumps