Reasons for mumps outbreaks in vaccinated population remain unclear
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CDC researchers reported data on 2,503 sixth- through 12th-grade students from three schools in an Orthodox Jewish community in Orange County, N.Y., where a mumps outbreak occurred in 2009. All of the students had documented two doses of mumps-containing vaccine. A total of 320 vaccinated children developed mumps.
The researchers said the children’s risk for mumps increased commensurately with the number of children in the class who had illness. Age at first dose; time since last dose; time between first and second dose; school; class size; number of hours at school per week; and household size were not associated with having mumps.
“Similar outbreaks among highly vaccinated populations have occurred in high-density settings, like universities and schools,” Preeta K. Kutty, MD, MPH, told Infectious Disease News.
In this study, the authors reported that “it may be less likely that waning immunity played a significant role as the median age group was lower than the previous college outbreaks as the time since last dose was not a significant factor,” the researchers wrote.
The investigators said the study findings highlight a need for further research into why mumps outbreaks occur and what preventive measures are required in such instances.
The study researchers concluded that two doses of mumps-containing vaccine may not be effective during an outbreak because of multiple, prolonged and intense exposure to the mumps virus.
Preeta K. Kutty, MD, MPH, MS, can be reached at the CDC, C25, 1600 Clifton Road, Atlanta, GA 30333; email: pkutty@cdc.gov.
Disclosure: The researchers report no relevant financial disclosures.