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States that easily grant immunization exemptions have higher incidence of whooping cough

October 11, 2006

States that have personal belief exemptions for school immunization requirements, and exemptions that are easily obtained, have higher rates of new cases of pertussis (whooping cough) than states in which obtaining immunization exemptions is more difficult, according to a study in the October 11 issue of JAMA.

State-mandated school immunization requirements have played a major role in achieving and maintaining low rates of vaccine-preventable diseases in the United States. All states and the District of Columbia require children entering school to provide documentation that they have met the state vaccine requirements, according to background information in the article. As of March 2006, all states permitted medical exemptions to school and daycare immunization requirements; 48 states allowed religious exemptions; and 19 states had a provision for personal belief exemptions, such as religious, philosophical, and any other unspecified nonmedical exemption.

States that make exemptions widely available to parents, either by offering a personal belief exemption or making the exemption option easy to obtain, may have higher rates of exemptions or may experience substantial increases in exemption rates. Increasing exemption rates can increase individual and community risk to vaccine-preventable diseases, the authors write. The role of exemption policies may be especially important for pertussis, which remains present in certain areas of the United States and has been increasing in incidence during the past decade.

Saad B. Omer, M.B.B.S., M.P.H., of the Johns Hopkins Bloomberg School of Public Health, Baltimore, and colleagues conducted a study to determine if the rates of nonmedical exemptions differ and have been increasing in states that offer only religious vs. personal belief exemptions, and if the incidence of pertussis is associated with policies of granting personal belief exemptions and ease of obtaining exemptions. The researchers analyzed state-level rates of nonmedical exemptions at school entry from 1991 through 2004 and data for incidence of pertussis from 1986 through 2004 for individuals age 18 years or younger.

From 2001 through 2004, states that permitted personal belief exemptions had higher nonmedical exemption rates than states that offered only religious exemptions, and states that easily granted exemptions had higher nonmedical exemption rates in 2002 through 2003 compared with states with medium and difficult exemption processes. The average exemption rate increased an average of 6 percent per year from 1991 to 2004 among states that offered personal belief exemptions. In states that easily granted exemptions, the rate increased 5 percent per year from 1991 to 2004. No statistically significant change was seen in states that offered only religious exemptions or that had medium and difficult exemption processes. However, the researchers also found that easier granting of exemptions was associated with a 53 percent increased incidence of pertussis, and the availability of personal belief exemptions was associated with a 48 percent increased incidence.

"States must balance parental autonomy with the tremendous public health benefit of vaccines when considering the types of exemptions allowed and how policies are implemented. An approach similar to the model applied to conscientious objectors to [military] conscription, which focuses on the sincerity of the applicants' beliefs and includes administrative controls, may provide a reasonable middle ground. Our findings support the need for effective administrative controls over granting nonmedical exemptions. Moreover, state-level policies on nonmedical exemptions and documentation of immunization status should be viewed as part of the efforts to control or eliminate vaccine-preventable diseases," the authors conclude.

JAMA and Archives Journals