*4.1. Comparison with Other Research*

This study identified similar determinants of vaccine inequality as has been observed across other qualitative and quantitative research on drivers of immunization coverage and equity, including access, cost, health systems readiness, gender-related barriers, vaccine supply, fear of side effects, community engagement, lack of knowledge, and provider absenteeism [3–5,10]. Our study contributes to this literature by identifying the relationships among these barriers and how those interactions contribute to no vaccination or under-vaccination. As noted in the recent systematic review of vaccination barriers by Kaufman [7], less than half of all global studies report barriers across all determinants of vaccination, but our study was designed to holistically and comprehensively explore barriers from the perspective of caregivers. A handful of published studies use HCD approaches to study vaccination barriers and solutions, including ones from Mozambique [19], India [30], and the Philippines [31]. The Mozambique study identified similar patterns of barriers to vaccination, including the role of gender barriers and power imbalances with health workers. Cross-national quantitative analyses of household survey data show that immunization inequalities are associated with household wealth and maternal education [6], and that the prevalence of zero-dose children is associated with gender inequality [8], birth order, birth weight, maternal education, maternal occupation, household wealth, and the number of antenatal care visits [9].
