Inequalities in full immunization coverage among one-year-olds in the Democratic Republic of the Congo, 2007-2017.

BACKGROUND

The Democratic Republic of the Congo (DRC) ranks among the top ten countries with the highest rates of zero-dose or partially immunized children. However, there is limited knowledge about the extent of inequalities in full immunization coverage. This study assessed the extent and trends of inequalities in full immunization coverage among one-year-olds.

METHODS

We used data from the 2007 and 2013 rounds of the DRC Demographic and Health Surveys, as well as from the 2010 and 2017 rounds of the DRC Multiple Indicator Cluster Surveys. In this study, full immunization coverage was defined as the percentage of one-year-olds who received one dose of the Bacillus Calmette-Guérin vaccine, three doses of the polio vaccine, three doses of the combined diphtheria, tetanus toxoid and pertussis vaccine, and one dose of the measles-containing vaccine. The data were disaggregated into four dimensions of inequality: economic status, maternal education, place of residence, and subnational region. For each dimension, we analysed inequality using four measures: Difference (D), Population Attributable Risk (PAR), Ratio (R), and Population Attributable Fraction (PAF). Each point estimate of inequality was calculated with a 95% confidence interval using bootstrap methods. Analyses were performed using version 5.0 of the World Health Organization’s Health Equity Assessment Toolkit software.

RESULTS

The national coverage of full immunization among one-year-olds significantly decreased from 30.7% in 2007 to 21.7% in 2017. Significant disparities in full immunization coverage across the four dimensions of inequality were observed in all study periods. In 2017, for example, we recorded substantial economic (PAR = 18.1, 95% CI[ 16.3, 19.9]; PAF = 83.4, 95% CI[75.1, 91.8]), maternal education-based (PAR = 6.3, 95% CI[4.0, 8.7]; PAF = 29.1, 95% CI[18.3, 40.0]), place of residence-based (PAR = 6.7, 95% CI[5.7, 7.7]; PAF = 30.9, 95% CI[26.1, 35.7]), and regional (PAR = 20.9, 95% CI[15.2, 26.6]; PAF = 96.4, 95% CI[70.2, 122.6]) inequalities in full immunization coverage. Economic, urban‒rural, and regional relative inequalities followed a U-shaped trend, while absolute inequalities remained constant or decreased. However, inequality based on maternal education remained constant across all summary measures over time.

CONCLUSIONS

The decreasing trend of the National full immunization coverage among one-year-olds over the ten-year study period masked substantial and persistent socioeconomic and geographic inequalities revealed by this study. To reduce inequalities in full immunization coverage in the DRC, urgent equity-driven interventions are needed to address poverty, illiteracy, and inadequate infrastructure, particularly in rural and underserved regions. Strengthening the health workforce and improving the vaccine supply chain are crucial to ensuring equitable access to immunization services.