Bayesian spatial analysis of incomplete vaccination among children aged 12-23 months in Nigeria

High childhood disease prevalence and under-five mortality rates have been consistently reported in Nigeria. Vaccination is a cost-effective preventive strategy against childhood diseases. Therefore, this study aimed to identify the determinants of Incomplete Vaccination (IV) among children aged 12-23 months in Nigeria. This cross-sectional design study utilized the 2018 Nigeria Demographic and Health Survey (NDHS) dataset. A two-stage cluster sampling technique was used to select women of reproductive age who have children (n = 5475) aged 12-23 months. The outcome variable was IV of children against childhood diseases. Data were analyzed using Integrated Nested Laplace Approximation and Bayesian binary regression models (α_0.05). Visualization of incomplete vaccination was produced using the ArcGIS software. Children's mean age was 15.1 ± 3.2 months and the median number of vaccines received was four. Northern regions contributed largely to the IV. The likelihood of IV was lower among women aged 25-34 years (aOR = 0.67, 95% CI = 0.54-0.82, p < 0.05) and 35-49 years (aOR = 0.59, 95%CI = 0.46-0.77, p < 0.05) compared to younger women in the age group 15-24 years. An increasing level of education reduces the risk of odds of IV. Other predictors of IV were delivery at the health facility (aOR = 0.64, 95% CI = 053-0.76, p < 0.05), and media exposure (aOR = 0.63, 95%CI = 0.54-0.79, p < 0.05). Mothers' characteristics explained most of the variability in the IV, relatively to smaller overall contributions from the community and state-level factors (p < 0.05). The level of IV against childhood diseases was high in Nigeria. However, disparities exist across the regions and other socioeconomic segments of the population. More efforts are required to improve vaccination sensitization programs and campaigns in Nigeria.