This study examined the potential for changes in laws regarding exemptions from state immunization requirements to affect public health risks of communicable diseases. Although all states require immunizations for public school attendance, they must allow for individual medical exemptions; the legality of philosophical exemptions, often granted for religious reasons, is variable among states. Arkansas allowed philosophical exemptions in 2003. The authors looked at data from the Arkansas Department of Health from 2001–2002, before the ruling was made. They compared this information to data from 2003–2004 to understand where exemptions were being made and whether those exemptions changed considerably in number after the 2003 ruling. In 2005 pediatric immunization rates in Arkansas were among the lowest in the nation for children 19–35 months (64.2%, compared to 76.1% nationally).
The data showed that the total number of exemptions increased 23 percent from 2001 to 2002; 17 percent from 2002–2003, the first year philosophical exemptions were allowed; and by 50 percent from 2003–2004. As a proportion of total exemptions, nonmedical exemptions increased by 79 percent, 92 percent and 95 percent in those years. Because exemptions were increasing before the law allowing nonmedical exemptions was passed in 2003, it is not possible to know exactly how much of the subsequent increase is due to an ongoing trend, and how much is due to the changed law. The fact that as nonmedical exemptions increased, medical ones decreased suggests that medical exemptions may have been used to avoid immunization. These data also suggest a possibly growing resistance to immunization that is not based on religious beliefs. The geographical clustering of the nonmedical exemptions similarly supports the conclusion that nonmedical reasons, such as fears about vaccine safety, are behind increases in refusals to vaccinate. States that offer only religious exemptions and not philosophical exemptions have not experienced increases in requests.
The potential public health risks due to the increasing number of unvaccinated children are obvious. For example, 93 percent to 95 percent vaccine coverage is necessary to avoid a measles outbreak in children. Recent outbreaks of mumps also have occurred. The authors conclude that increased numbers of unvaccinated children due to philosophical exemptions is a public health risk that remains largely under the radar of physicians and of the public. Such risks need to be communicated to health care providers and to communities at large. Additionally, the fact that numerous studies have failed to support adverse sequelae of vaccination needs to be clearly communicated to parents.