During 2010-2011, varicella vaccination was an added requirement for school entrance in Wyoming. Vaccination exemption rates were compared during the 2009-2010 and 2011-2012 school years, and impacts of implementing a new childhood vaccine requirement were evaluated. All public schools, grades K-12, were required to report vaccination status of enrolled children for the 2009-2010 and 2011-2012 school years to the Wyoming Department of Health. Exemption data were analyzed by exemption category, vaccine, county, grade, and rurality. The proportion of children exempt for =1 vaccine increased from 1.2% (1,035/87,398) during the 2009-2010 school year to 1.9% (1,678/89,476) during 2011-2012. In 2011, exemptions were lowest (1.5%) in urban areas and highest (2.6%) in the most rural areas, and varicella vaccine exemptions represented 67.1% (294/438) of single vaccination exemptions. Implementation of a new vaccination requirement for school admission led to an increased exemption rate across Wyoming.