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Estimated MMR vaccination rates as low as 50% among Disneyland outbreak population
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Vaccination rates among those exposed to the recent measles outbreak linked to Disneyland theme parks are estimated to be as low as 50% and no higher than 86%, according to study findings in JAMA Pediatrics.
"Although the index case has not yet been identified, the outbreak likely started sometime between Dec. 17 and 20, 2014. Rapid growth of cases across the United States indicates that a substantial percentage of the exposed population may be susceptible to infection due to lack of, or incomplete, vaccination," study researcher Maimuna S. Majumder, MPH, of Massachusetts Institute of Technology, and colleagues wrote.
Maimuna S. Majumder
As of March 6, there have been 173 cases of measles across 17 states and the District of Columbia, according to the CDC. Of these, 73% are related to the Disneyland outbreak.
To estimate vaccination rates among those affected by the ongoing outbreak, Majumder and colleagues utilized the incidence decay and exponential adjustment method along with cumulative incidence data from the California Department of Public Health.
Analysis indicated that measles-mumps-rubella vaccination rates among the exposed population could be as low as 50% and no higher than 86%.
Because of the highly contagious nature of measles, vaccination rates of 96% to 99% are necessary to preserve herd immunity and protect from outbreaks, according to the investigators.
"Clearly, MMR vaccination rates in many of the communities that have been affected by this outbreak fall below the necessary threshold to sustain herd immunity, thus placing the greater population at risk as well," they concluded. - by Amanda Oldt
Reference:
CDC. Measles cases and outbreaks. Available at: http://www.cdc.gov/measles/cases-outbreaks.html. Accessed March 13, 2015.
Disclosure : The researchers report no relevant financial disclosures.
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