Background: There is limited knowledge of the extent of or factors underlying inequalities in uptake of childhood vaccination in Ireland. This paper aims to measure and decompose socioeconomic inequalities in childhood vaccination in the Republic of Ireland.Methods: The analysis was performed using data from the first wave of the Growing Up in Ireland survey, a nationally representative survey of the carers of over 11,000 nine-month old babies collected in 2008 and 2009. Multivariate analysis was conducted to explore the child and parental factors, including socioeconomic factors that were associated with non-vaccination of children. A concentration index was calculated to measure inequality in childhood vaccination. Subsequent decomposition analysis identified key factors underpinning observed inequalities.Results: Overall the results confirm a strong socioeconomic gradient in childhood vaccination in the Republic of Ireland. Concentration indices of vaccination (CI = -0.19) show a substantial pro-rich gradient. Results from the decomposition analysis suggest that a substantial proportion of the inequality is explained by household level variables such as socioeconomic status, household structure, income and entitlement to publicly funded care (29.9%, 24% 30.6% and 12.9% respectively). Substantial differences are also observed between children of Irish mothers and immigrant mothers from developing countries.Conclusions: Vaccination was less likely in lower than in higher income households. Access to publicly funded services was an important factor in explaining inequalities. (C) 2014 Elsevier Ltd. All rights reserved.