In November 2007, a judge ordered parents of 2 300 students in Prince George County, Maryland, to appear at a special court hearing where they would have to allow their children to be vaccinated on the spot, provide proof that they already had vaccinated their children, obtain an exemption for religious or medical reasons, or face the possibility of fines or jail sentence. This dramatic event occurred after other efforts, such as phone calls and home visits, had failed to achieve compliance with state laws requiring immunization. Parents who refuse to immunize their children in Maryland are required to file for a state-approved exemption or make arrangements with the state allowing them to home school their children.1 This exercise of state power not only was effective, reducing the number of students out of compliance to less than 1 000, but also raised important questions about the balance between individual freedom and public health and the proper use of state power.
Nearly every public health measure has the potential to impinge upon individual freedom. Laws governing the water and food supply, controls on air pollution, legislative efforts to protect children from tobacco, mandatory immunization statutes, and the compelled treatment, isolation, or quarantine of persons with sexually transmitted diseases, tuberculosis, or other communicable diseases are examples of how government may regulate individual or corporate behavior to positively affect the health of a population. Balancing individual freedom with the protection of the population's health represents one of the most important ethical issues related to public health.
In general, public health officers can legally compel vaccination and other public health measures. But when the judge in Prince George County ordered parents of students to vaccinate their children, seek exemption, or face fines or jail sentence, he was placing serious limits on individual freedom, and doing so requires moral justification. For those working in public health, understanding the ethical underpinnings of state compulsion is essential for exercising judgment about when and how that power should be exercised. Compulsory immunization statutes represent just one manifestation of these trade-offs and the ethical issues surrounding many public health interventions.
The government's authority in the public health arena arises primarily from its constitutionally sanctioned "police power" to protect the public's health, welfare, and safety. These police powers can be abused, however, and should not be exercised without moral justification. The moral basis for these powers was the subject of John Stuart Mill's On Liberty. Mill argued, "The only purpose for which power can rightfully be exercised over any member of a civilized community, against his will, is to prevent harm to others. His own good, either physical or moral, is not a sufficient warrant."2(p13) Mill's justification for interfering with the freedom of an individual has become known as the harm principle, and it represents the moral basis for laws in liberal democracies such as the United States. The harm principle recognizes not only the importance of individual liberty but also that individual liberty can be constrained when its exercise harms others (and thus impinges on the individual liberty of those harmed). The harm principle justifies restrictions on individual liberty when individual decisions or actions put others at significant risk of serious harm, when harm can be prevented by restricting individual liberty, and when no less restrictive alternative would be equally effective at preventing the harm.3
Those with the power to exercise these police powers in the name of public health should ask not only whether the law will support interference with individual liberty in a given situation but also whether the exercise of those police powers satisfies the conditions of the harm principle. If it does not, the exercise of coercive power might not be ethically justifiable, even if it is legally authorized. Public health authorities may justifiably interfere with a parental decision to refuse immunization on behalf of a child in any situation where someone other than the parent is placed at significant risk of serious harm, where vaccinating the child will prevent that harm, and where no less intrusive alternative to forced vaccination would be effective at preventing the harm. Two distinct situations arise in which the conditions of the harm principle might be satisfied for childhood immunization. First, state intervention may be justified when there is evidence that parental actions or decisions are likely to harm the child. Second, intervention may be justified as an exercise of government's police powers when immunization is necessary to protect the health of others in the population.
Under most conditions in the United States, including those existing in Prince George County in 2007, it would be difficult to argue that an individual child without immunization has been placed at significant risk of serious harm. In those rare cases where the decision of a parent places the child at substantial risk of serious harm (ie, where a child has sustained a deep and contaminated puncture wound), state agencies may be justified in providing the necessary immunization over the parents' objections.
But the harm principle also justifies exercise of the state's police powers when an individual's action places others at substantial risk of serious harm. The state's duty to protect children attending public schools morally justifies most state laws that require immunization before school entry. Parents who choose not to immunize their children increase the potential for harm to other children at school-those who cannot be immunized because of medical conditions and the small percentage of vaccinated children who remain susceptible to disease. These individuals derive important benefit from herd immunity and are placed at risk of harm by those who remain unvaccinated by parental choice.
Most state "mandates," including those in Prince George County, also incorporate Feinberg's addition to the harm principle-that no option less intrusive to individual liberty would be equally effective at preventing the harm. These school entry requirements recognize that serious harm can be averted in most situations without compulsory immunization. In fact, most state mandates are not mandates at all, providing parents with opt-out provisions or allowing them to home school their children. These options fall short of true coercion and are less intrusive to individual liberty than truly forced immunization.
The judge and public health officials in Prince George County acted in accord with the moral tenets of the harm principle. They did not resort to coercion until all other efforts had failed. Parents had the option to file for a state-approved exemption or make arrangements with the state allowing them to home school their children. Phone calls and letters had failed to generate a response. Only those parents who had not responded to these noncoercive measures were required to appear before the court and threatened with jail sentence or fines. Even then, the reason for bringing them into court was not solely because they had failed to immunize their children but also because their children were not enrolled in school and no arrangements had been made for schooling. The judge rightly recognized this failure to arrange for education as also invoking the harm principle.
One final observation is necessary. Most public health measures, including child immunization laws and those relating to compulsory treatment, isolation, or quarantine for highly infectious diseases, exist primarily to protect individuals other than the person subject to the public health intervention. These public health measures are public goods, and individuals should not be asked to bear costs associated with these measures by themselves. Because all individuals in the community, including those refusing to immunize themselves or their children, benefit from immunization programs, the costs of these programs should be born by the public. Out-of-pocket costs for a full series of childhood immunizations can be as high as $650 for underinsured individuals.4 Charging individuals the cost of vaccines or administrative fees, or sending them elsewhere for immunizations, creates disincentives for parents to vaccinate their children. At the same time, it allows "free riders" to avoid the financial costs of a program that benefits them.
For these reasons, a strong argument can be made to fund immunization programs and other public health programs through a tax-based system. These programs represent a community good and they should be funded at public expense. They should include provision of adequate compensation for losses and healthcare due to vaccine-related injury or other coercive measures such as treatment, isolation, or quarantine after contact with highly contagious infectious diseases. Public health programs benefit all citizens. Justice requires that the burdens and benefits of public health intervention be shared across the population.
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