This study aimed to evaluate the trends and changes in inequities in the CPV scheduled before the first year of age among children aged 12–23 months, from 2000 to 2017.

Data were extracted from five rounds of the PVCS. The household income per month was an index of socioeconomic status for the inequity analysis. Researchers used the CI to quantify the degree of inequity, and the decomposition approach was applied to quantify the contributions from independent factors to injustice in the CPV.

The CPV was significantly improved from 2000 to 2017, with 67.0% for the 2000 PVCS and 86.0% for the 2017 PCVS. The CI value decreased from 0.29839 for the 2000 round to 0.03601 for the 2017 round. The decomposition analysis indicated that independent variables such as birth order, ethnic group, mother’s education, maternal employment status, residence, immigration status, and the percentage of the total health spending allocated to public health could explain the inequity in the CPV in varying degrees.

The study concluded that a sharp reduction in socioeconomic inequity in the CPV was from 2000 to 2017. Policy recommendations to reduce the inequality in the CPV should focus on children with the risk factors found in this study for a better outcomes in complete vaccination and long-lasting herd immunity.