Decomposition of socioeconomic inequalities in zero-dose children aged 12–23 months in India

Children who do not receive the preliminary dose of the DTP-containing vaccine are likely to be known as zero-dose, occurring due to limited access to healthcare services and several sociodemographic patterns. In India, 6.67% points (pp) of children remain zero-dose, and a significant inequality exists due to socioeconomic factors. Therefore, this study measures the magnitude of the socioeconomic gap and quantifies the key determinants that contribute to the zero-dose inequality using the National Family Health Survey fifth round (NFHS-5) data. A cross-sectional sampling data of 41,132 children aged 12-23 months was considered to employ several descriptive statistics, including a chi-squared test. We utilized the Wagstaff concentration curve (WCC) and concentration index (WCI) to represent the zero-dose inequality. Afterwards, WCI was decomposed to determine the major contributing factors to the socioeconomic gap in zero-dose. The overall prevalence of zero-dose children was 6.67 pp, and a socioeconomic gap in zero-dose by the household wealth index was 3.68 pp between the poorest and the richest. The WCI value for zero-dose due to the wealth index was - 0.12 (p < 0.001), revealed 25.15% of the inequality was contributed by the wealth index, 12.48% by maternal education, 11.57% by media exposure, 10.74% by antenatal care (ANC) visits, and 10.05% by place of children's delivery. To reduce zero-dose among children, multi-dimensional interventions and strategies are needed to address not only economic deprivation but also disparities in maternal health education, access to healthcare, and informational reach. While wealth-related inequality is evident, the wealth index captures broader household assets and living conditions beyond income. Similarly, media exposure may reflect extended access to health-related knowledge, including immunization. Strengthening maternal education, improving ANC coverage, enhancing service delivery, and outreach in underserved areas are crucial steps toward equitable immunization coverage.