Watching the Words Change Into Numbers: Consequences of Vaccine Exemption Laws

Background:  All 50 states allow medical exemptions to school vaccine requirements; 48 also permit religious exemptions.  Exemptions based on philosophical beliefs are relatively new, and are allowed in 20 states.  The effect of philosophical exemptions on vaccine exemption rates is unclear.

Objectives:  To examine differences in vaccine exemption rates by state and type of vaccine exemption permitted.

Methods:  States reporting vaccination data to CDC as part of the annual school report on vaccination requirements for the 2009-2010 school year were categorized by type of exemption permitted.  The proportion of exemptions was calculated for each category (medical only, medical and religious, medical, religious and philosophical) and compared using chi-square analyses.  Rate ratios were calculated.

Results:  The exemption rate among kindergarteners in states allowing only medical exemptions is 4.14 per 1,000 compared with 13.92 per 1,000 in states allowing medical and religious exemptions and 27.33 per 1,000 in states allowing medical, religious, and philosophical exemptions (p<0.001).  Kindergarteners have exemption rates 3.36 (95% CI: 3.01, 3.75) and 6.60 (5.96, 7.30) times greater in states with medical and religious exemptions and medical, religious and philosophical exemptions, respectively, compared to states allowing only medical exemptions.  Exemption rates among middle schoolers were 1.26 per 1,000, 8.95 per 1,000, and 28.39 per 1,000 in states allowing medical only, medical and religious, and medical, religious and philosophical exemptions, respectively (p<0.001).  Middle school students have exemption rates 7.13 (4.55, 11.18) and 22.61 (14.43, 35.45) times higher in states allowing medical and religious exemptions and states allowing medical, religious, and philosophical exemptions, respectively, compared with states allowing medical exemptions only.

Conclusions:  States that allow philosophical exemptions have higher exemption rates than states that do not; the effect this has on vaccination coverage is not known.  As additional states pass philosophical exemption laws, the potential increase in the number of children with vaccine exemptions is concerning.