摘要：Objectives. Our goal was to determine whether school-level variability in implementation of immunization requirements is associated with the likelihood of a child having received an exemption to school immunization requirements. Methods . We surveyed 1000 school immunization personnel in Colorado, Massachusetts, Missouri, and Washington. We explored associations between school implementation of immunization requirements and the likelihood of a child having an exemption using logistic regression models. Results . School policies associated with an increased likelihood of children having exemptions included lack of provision of written instructions for completing the school immunization requirement before enrollment, administrative procedures making it easier to claim an exemption, and granting of philosophical exemptions. In the 2 states we surveyed where philosophical exemptions are not authorized (Massachusetts and Missouri), 17.0% and 18.1% of schools reported permitting philosophical exemptions. Conclusions . Inconsistencies in the interpretation and implementation of school immunization laws contribute to variability in rates of exemptions. School policies should be reviewed to ensure consistency with the intent of state laws. Laws requiring that children be immunized before they begin school have contributed to a 98% to 100% reduction in the incidence of most vaccine-preventable diseases (VPDs). 1 Schools have been sites of transmission for measles, pertussis, varicella, and other VPDs. State immunization laws provide a safety net for immunization programs, ensuring that nearly all school-aged children are vaccinated. These laws demonstrate a public commitment to vaccination. As noted by Dr Walter Orenstein, former director of the National Immunization Program, “school laws establish a system for immunization, a system that works year in and year out regardless of political interest, media coverage, changing budget situations, and the absence of vaccine-preventable disease outbreaks to spur interest.” 2 (pS23) Currently, all states require documentation of vaccination for school entry, and many states have laws requiring vaccination for licensed child care and college entry. Some state laws specify which vaccines and how many doses are required, while other states authorize the state health officer or health board to determine the details of vaccination requirements. 3 All states permit exemptions for individuals who have medical contraindications to vaccination. To qualify for medical exemptions, parents or guardians usually obtain a letter or other documentation from a physician. Some states also allow nonmedical exemptions, generally categorized as religious or philosophical. The distinctions between these exemptions have been controversial, and some groups have attempted in recent years to broaden state religious exemptions to include philosophical exemptions. 3, 4 At present, 48 states permit religious exemptions (all but Mississippi and West Virginia), and 19 permit philosophical or personal exemptions. 5, 6 Two earlier studies documented the relationship between exemptions and increased risk of VPDs during the 1980s and 1990s. One of these studies showed that exempt children in Colorado were 22 times more likely to contract measles and about 6 times more likely to contract pertussis than vaccinated children. 7 The other, a national study, showed that exempt children were 35 times more likely to contract measles than vaccinated children. 8 Children who cannot be immunized for medical reasons, children who are too young to be vaccinated, and the few who do not respond to vaccines are at risk of contracting VPDs from unimmunized children with exemptions. In the Colorado study, schools that had pertussis outbreaks had a higher percentage of exempted children than schools without outbreaks (4.7% vs 1.3%; P <.001). 7 At least 11% of children who developed measles after having received 1 dose of vaccine were infected through contact with an exempted child. 7 A study conducted by Rota et al. explored state variability in implementation of immunization requirements and associations between state policies and procedures and state exemption rates. 9 This study revealed that the complexity of paperwork or effort required to complete the exemption process was inversely related to the proportion of exemptions filed. In the present study, we sought to determine (1) within-state variability in implementation of immunization requirements and (2) associations between school policies or procedures and the likelihood of a child having an exemption.
