Socioeconomic inequalities in child vaccination in low/middle-income countries: what accounts for the differences?

Background Socioeconomic inequalities in child vaccination continue to be a global public health concern. This study aimed to measure and identify factors associated with socioeconomic inequalities in full immunisation coverage against the four core vaccine-preventable diseases (ie, bacille Calmette-Guerin, diphtheria-tetanus-pertussis (three doses), polio (three doses) and measles vaccines) in 46 low/middle-income countries. Methods The most recent nationally representative samples of children (aged 10-59 months, n=372 499) collected through the Demographic Health Surveys were used to measure vaccination rates. The concentration index (C) was used to quantify socioeconomic inequalities in vaccination coverage. Furthermore, meta-regression analyses were used to determine factors affecting socioeconomic inequalities in vaccination coverage across countries. Results Results suggested that immunisation coverage was pro-rich in most countries (median C=0.161, IQR 0.131). Gambia (C=-0.146, 95% CI -0.223 to -0.069), Namibia (C=-0.093, 95% CI -0.145 to -0.041) and Kyrgyz Republic (C=-0.227, 95% CI -0.304 to -0.15) were the only countries where children who belong to higher socioeconomic status group were less likely to receive all the four core vaccines than their lower socioeconomic status counterparts. Meta-regression analyses suggested that, across countries, the concentration of antenatal care visits among wealthier mothers was positively associated with the concentration of vaccination coverage among wealthier children (coefficient=0.606, 95% CI 0.301 to 0.911). Conclusions Pro-rich distribution of child vaccination in most low/middle-income countries remains an important public health policy concern. Policies aimed to improve antenatal care visits among mothers in lower socioeconomic groups may mitigate socioeconomic inequalities in vaccination coverage in low/middle-income countries.