A longitudinal analysis of the effect of non-medical exemption laws and vaccine uptake on vaccine-targeted disease rates

Public health officials are concerned about outbreaks of vaccine-targeted diseases (VTDs) and increased use of non-medical exemptions (NME) for mandatory vaccines. This project estimated the effects of NME law restrictiveness and vaccine uptake for required school/childcare entry vaccines on incidence rates for five VTDs – Pertussis, Measles, Mumps, Haemophilus Influenzae Type B (Hib), and Hepatitis B. State-level longitudinal mixed-effects regression models were used to examine 2000-2008 NNDSS incidence data. Key explanatory variables were state-level vaccine-specific uptake rates and state NME law restrictiveness measured on a five-point scale.

The results show that Pertussis incidence was negatively associated with NME law restrictiveness and DTaP vaccine uptake, suggesting a positive association with NME use. However, Hepatitis B, Hib, Measles and Mumps incidence was not associated with either state NME law restrictiveness or vaccine uptake. The pertussis finding suggests that increasing state NME restrictiveness by one level would decrease mean annual national pertussis incidence by 1.14 percent, approximately 171 fewer cases. Additionally, increasing national DTaP vaccine uptake by one percent would decrease annual national pertussis incidence by approximately five cases.

State NME regulatory environments and vaccine uptake appear to influence pertussis incidence rates but not other VTDs with relatively low incidence. Additional research is needed to better understand potential underlying mechanisms by which various NME law characteristics affect particular disease incidence rates. The effect of law may depend on disease incidence thresholds. Analysis is needed to evaluate the potential public health, legal, economic and social implications of adopting various legislative solutions.