Decomposing socioeconomic inequality in child vaccination in the Gambia, the Kyrgyz Republic and Namibia.

Extant work suggested pro-rich distribution of vaccination coverage in low- and middle-income countries (LMICs). However, the current literature also suggested pro-poor distribution of vaccination in some countries, including the Gambia, the Kyrgyz Republic and Namibia. This study aimed to explain socioeconomic inequalities in the completion rate of the four-core vaccines (i.e., Bacille Calmette-Guérin [BCG], diphtheria-tetanus-pertussis [DTP, 3 doses], Polio [3 doses] and Measles vaccines) in the three aforementioned countries. We used the most recent available Demographic Health Surveys (DHS) to measure vaccination completion rates among children (aged 0-59 months, n = 16,752) in the three countries. The normalized concentration index (Cn) was used to quantify and decompose socioeconomic inequalities in vaccination coverage in each country. The negative values of the Cn index suggested that children belong to lower socioeconomic status groups were more likely to be immunized than their higher socioeconomic status counterparts in the Gambia (Cn = -0.101, 95% confidence interval [CI]: -0.128 to -0.074), the Kyrgyz Republic (Cn = -0.097, 95% CI: -0.13 to -0.063) and Namibia (Cn = -0.161, 95% CI: -0.199 to -0.124). The decomposition analysis of the Cn suggested that the difference in child vaccination completion rates between rural and urban areas was the main factor contributing to the concentration of child vaccination among the poor in the Gambia and Namibia. The concentration of child vaccination among the poor in the Kyrgyz Republic was chiefly determined by household wealth. These results suggest that there should be strategies to improve child immunization uptake among urban children in the Gambia and Namibia. Since household wealth was the main factor contributing to the observed pro-poor distribution of child vaccination in the Kyrgyz Republic, further studies are required to understand the reasons for lower vaccination rate among the wealthy children in order to implement the most effective strategies to increase child vaccination uptake.