Measles Outbreak in a Highly Vaccinated Population, San Diego, 2008: Role of the Intentionally Undervaccinated

Epidemic Intelligence Service, Office of Workforce and Career Development, Centers for Disease Control and Prevention, 1600 Clifton Rd NE, Mail Stop E-05, Atlanta, GA 30333, USA.
PEDIATRICS (Impact Factor: 5.47). 03/2010; 125(4):747-55. DOI: 10.1542/peds.2009-1653
Source: PubMed


In January 2008, an intentionally unvaccinated 7-year-old boy who was unknowingly infected with measles returned from Switzerland, resulting in the largest outbreak in San Diego, California, since 1991. We investigated the outbreak with the objective of understanding the effect of intentional undervaccination on measles transmission and its potential threat to measles elimination.
We mapped vaccination-refusal rates according to school and school district, analyzed measles-transmission patterns, used discussion groups and network surveys to examine beliefs of parents who decline vaccination, and evaluated containment costs.
The importation resulted in 839 exposed persons, 11 additional cases (all in unvaccinated children), and the hospitalization of an infant too young to be vaccinated. Two-dose vaccination coverage of 95%, absence of vaccine failure, and a vigorous outbreak response halted spread beyond the third generation, at a net public-sector cost of $10 376 per case. Although 75% of the cases were of persons who were intentionally unvaccinated, 48 children too young to be vaccinated were quarantined, at an average family cost of $775 per child. Substantial rates of intentional undervaccination occurred in public charter and private schools, as well as public schools in upper-socioeconomic areas. Vaccine refusal clustered geographically and the overall rate seemed to be rising. In discussion groups and survey responses, the majority of parents who declined vaccination for their children were concerned with vaccine adverse events.
Despite high community vaccination coverage, measles outbreaks can occur among clusters of intentionally undervaccinated children, at major cost to public health agencies, medical systems, and families. Rising rates of intentional undervaccination can undermine measles elimination.

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    • "From a review of the literature on the economic impact of measles outbreaks in the US [11] [12] [13] [14], we collated data on the reallocation of personnel and resources for the outbreak response (including investigation, contact tracking, screening, laboratory work, emergency response and surveillance) as well as associated costs incurred by local and state public health departments; specifically, we retrieved data on the number of cases reported in these outbreaks, the number of contacts (or exposures to measles cases) identified, the number of hours allocated by local and state responders, and the main activities performed during the outbreak investigations and response (Table 1). Particular attention was given to studies that reported number of personnel hours allocated to the response by local and/or state health department and associated personnel costs. "
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    ABSTRACT: Despite vaccination efforts and documentation of elimination of indigenous measles in 2000, the United States (US) experienced a marked increase in imported cases and outbreaks of measles in 2011. Due to the high infectiousness and potential severity of measles, these outbreaks require a vigorous response from public health institutions. The effort and resources required to respond to these outbreaks are likely to impose a significant economic burden on these institutions. To estimate the economic burden of measles outbreaks (defined as ≥3 epidemiologically linked cases) on the local and state public health institutions in the US in 2011. From the perspective of local and state public health institutions, we estimated personnel time and resources allocated to measles outbreak response in local and state public health departments, and estimated the corresponding costs associated with these outbreaks in the US in 2011. We used cost and resource utilization data from previous studies on measles outbreaks in the US and, relying on outbreak size classification based on a case-day index, we estimated costs incurred by local and state public health institutions. In 2011, the US experienced 16 outbreaks with 107 confirmed cases. The average duration of an outbreak was 22 days (range: 5-68). The total estimated number of identified contacts to measles cases ranged from 8936 to 17,450, requiring from 42,635 to 83,133 personnel hours. Overall, the total economic burden on local and state public health institutions that dealt with measles outbreaks during 2011 ranged from an estimated $2.7 million to $5.3 million US dollars. Investigating and responding to measles outbreaks imposes a significant economic burden on local and state health institutions. Such impact is compounded by the duration of the outbreak and the number of potentially susceptible contacts.
    Vaccine 10/2013; 32(11). DOI:10.1016/j.vaccine.2013.10.012 · 3.62 Impact Factor
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    • "A change in the belief of these groups and professionals will be a necessary step to accomplish measles elimination [29]. Attaining an overall vaccine coverage of 95% will not suffice if clusters of unvaccinated persons persevere [30] even if these clusters are small [31]. The policy to exclude unvaccinated students from school during an outbreak has proven to be successful in previous outbreaks [5], but is probably unfeasible in this setting. "
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    ABSTRACT: From Mid-February to April 2011 one of the largest measles-outbreak in Flanders, since the start of the 2-dose vaccination scheme in 1995, took place in Ghent, Belgium. The outbreak started in a day care center, infecting children too young to be vaccinated, after which it spread to anthroposophic schools with a low measles, mumps and rubella vaccination coverage. This report describes the outbreak and evaluates the control measures and interventions. Data collection was done through the system of mandatory notification of the public health authority. Vaccination coverage in the schools was assessed by a questionnaire and the electronic immunization database 'Vaccinnet'. A case was defined as anyone with laboratory confirmed measles or with clinical symptoms and an epidemiological link to a laboratory confirmed case. Towards the end of the outbreak we only sought laboratory confirmation for persons with an atypical clinical presentation or without an epidemiological link. In search for an index patient we determined the measles IgG level of infants from the day care center. A total of 65 cases were reported of which 31 were laboratory confirmed. Twenty-five were confirmed by PCR and/or IgM. In 6 infants, too young to be vaccinated, only elevated measles IgG levels were found. Most cases (72%) were young children (0--9 years old). All but two cases were completely unimmunized. In the day care center all the infants who were too young to be vaccinated (N=14) were included as cases. Thirteen of them were laboratory confirmed. Eight of these infants were hospitalized with symptoms suspicious for measles. Vaccination coverage in the affected anthroposophic schools was low, 45-49% of the pupils were unvaccinated. We organized vaccination campaigns in the schools and vaccinated 79 persons (25% of those unvaccinated or incompletely vaccinated). Clustering of unvaccinated persons, in a day care center and in anthroposophic schools, allows for measles outbreaks and is an important obstacle for the elimination of measles. Isolation measures, a vacation period and an immunization campaign limited the spread of measles within the schools but could not prevent further spread among unvaccinated family members. It was necessary to raise clinicians' awareness of measles since it had become a rare, less known disease and went undiagnosed.
    Archives of Public Health 07/2013; 71(1):17. DOI:10.1186/0778-7367-71-17
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    • "Increasing public concern about the safety of vaccinations has led some parents to decline or delay immunization of their children . Recent outbreaks of measles, mumps and pertussis in the United States are an important reminder of how immunization delays and refusals can have a significant impact on vaccine preventable diseases [9] [10] [11] [12] [13]. In a recent study of parental concerns regarding vaccination, more than half of the respondents reported concerns about potential serious adverse events following immunization (AEFI) and one out of every eight respondents reported refusing a vaccine recommended by their physician [14]. "
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    ABSTRACT: A number of new and combination vaccines have been introduced for children in the past two decades. Encephalitis cases occurring within defined time windows following administration of pertussis- or measles-containing vaccines are eligible for compensation by the Vaccine Injury Compensation Program. Due to increased parental concerns about vaccine safety and potential neurologic adverse events following immunization with new and multiple vaccines administered at the same visit, our aim was to determine whether immunizations are associated with an increased risk of encephalitis within defined risk windows. We reviewed immunization records from 246 pediatric encephalitis cases referred to the California Encephalitis Project between July 1998 and December 2008. We included data on 110 cases who had been immunized in the year prior to the onset of encephalitis (observation period) and had complete immunization records. We used the case-centered method to test whether cases were more likely to have developed encephalitis in defined risk windows-42, 30 and 21 days after any vaccination, 3 days after pertussis-containing vaccines and 5-15 days after measles-virus containing vaccines-compared with the rest of the observation period. All vaccines recommended in the current immunization schedule were represented in our sample. No increased risk of encephalitis was seen following administration of pertussis-containing vaccines, measles-containing vaccines or any number of vaccines administered in a single visit (vaccine episode); the odds ratios and 95% confidence intervals for encephalitis after a vaccine episode were: 1.0 (0.6-1.8) in a 42-day risk window, 0.9 (0.5-1.6) in a 30-day risk window and 1.2 (0.7-2.2) in a 21-day risk window. No association between receipt of currently recommended immunizations and subsequent development of encephalitis was observed in this study.
    Vaccine 11/2011; 30(2):247-53. DOI:10.1016/j.vaccine.2011.10.104 · 3.62 Impact Factor
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