Exemptions from mandatory immunization after legally mandated parental counseling

Background: The success of health care provider counseling-based interventions to address vaccine hesitancy is not clear. In 2011, Washington State implemented Senate Bill 5005 (SB5005), requiring counseling and a signed form from a licensed health care provider to obtain an exemption. Evaluating the impact of a counseling intervention can provide important insight into population-level interventions that focus on interpersonal communication by a health care provider. Methods: We used segmented regression and interaction and aggregation indices to assess the impact of SB5005 on immunization coverage and exemption rates in Washington State from school years 1997-1998 through 2013-2014. RESULTS: After SB5005 was implemented, there was a significant relative decrease of 40.2% (95% confidence interval: -43.6% to -36.6%) in exemption rates. This translates to a significant absolute reduction of 2.9 percentage points (95% confidence interval: -4.2% to -1.7%) in exemption rates. There were increases in vaccine coverage for all vaccines required for school entrance, with the exception of the hepatitis B vaccine. The probability that kindergarteners without exemptions would encounter kindergarteners with exemptions (interaction index) decreased, and the probability that kindergarteners with exemptions would encounter other such kindergarteners (aggregation index) also decreased after SB5005. Moreover, SB5005 was associated with a decline in geographic clustering of vaccine exemptors. CONCLUSIONS: States in the United States and jurisdictions in other countries should consider adding parental counseling by health care provider as a requirement for obtaining exemptions to vaccination requirements.