Associations of daycare and school entry vaccination requirements with varicella immunization rates.

School and daycare entry requirements have been credited with increasing immunization rates among school-age children, but no prior study has assessed the nationwide effects of entry requirements while controlling for individual, family, and household characteristics. The 2002 National Immunization Survey (NIS) is a nationally representative annual survey that includes provider record-verified immunization dates for 20,546 children aged 19-35 months without prior history of varicella. In weighted bivariate and multivariate logistic regression models, we examined the association of state entry mandate implementation with children's up-to-date (UTD) status for varicella vaccine, adjusted for sociodemographic characteristics of children, mothers, and household income and for children's UTD status for other recommended vaccines. In this national sample representative of 5.6 million children, 83.2% (95% CI: 82.3%-84.1%) were UTD for varicella vaccine. Between 1997 and 2002 inclusive, 33 states and the District of Columbia had implemented school and/or daycare entry immunization mandates for varicella. In bivariate analyses, 84.9% (83.9%-85.9%) of children in states with varicella entry mandates were UTD, compared to 76.8% (75.3%-78.4%) of children in states without such mandates. In multivariate analyses controlling for child and family characteristics, children living in states with varicella entry mandates remained significantly more likely to be UTD for varicella than children in states without mandates. These findings indicate that immunization entry requirements are associated with higher immunization rates among preschool-age children, and suggest that the effects of entry requirements are independent of other individual and household factors associated with childhood immunization.