Anatomy of a Measles Outbreak: The Impact of Vaccination Refusal
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Pharmacists who struggle to defend the benefits of immunization to parents fearful of adverse vaccine effects may be particularly interested in an article in the April 2010 issue of Pediatrics.
The article—authored by a group of state and national public health officials—describes the sequence of events that began when an intentionally unvaccinated 7-year-old boy from California was unknowingly infected with measles during a trip to Switzerland. The boy’s return to San Diego in January 2008 initiated the largest local outbreak of measles since 1991.
The authors sought to understand the effect of intentional undervaccination on measles transmission and its potential threat to measles elimination. In addition to analyzing measles-transmission patterns and mapping vaccination-refusal rates, the authors used discussion groups and network surveys to examine the beliefs of parents who decline vaccination.
The authors discovered that the measles outbreak was “fueled by clusters of intentionally unvaccinated children and perpetuated by delayed clinical diagnosis and inadequate infection-control measures.” A total of 839 people were exposed, and 11 unvaccinated children (in addition to the initial 7-year-old boy) were infected. Although eight of those children were intentionally unvaccinated, three were below the minimum age for vaccination, and one (a 10-month-old infant) had to be hospitalized for 72 hours and receive intravenous hydration for diarrhea.
The net public-sector costs to control the outbreak were estimated at more than $10,000 per case. The families of 73 unvaccinated children who were placed under 21-day quarantine reported average direct and indirect costs of $775 per quarantined child.
Intentional undervaccination appeared to be most prevalent in public charter and private schools, as well as in public schools in upper-socioeconomic areas. In discussion groups and survey responses, the majority of parents who declined vaccination for their children cited concern about vaccine adverse events.
Pediatrics. 2010;125:747-55.