Social Determinants of Health and Immune Response to Routine Childhood Vaccination

Background: Childhood vaccination remains one of the most effective public health interventions globally. However, variability in immune responses among vaccinated children suggests that factors beyond vaccine formulation and administration influence immunogenicity. Social determinants of health (SDOH) including household income, parental education, nutritional status, housing conditions, and access to healthcare—may modulate vaccine-induced immunity through complex biological and behavioral pathways. Despite growing recognition of health inequities, the relationship between SDOH and vaccine immunogenicity in children remains insufficiently characterized. Methods: A cross-sectional analytical study was conducted among 412 children aged 12–24 months attending primary healthcare centers in an urban setting. Sociodemographic data were collected using a structured questionnaire addressing household income, parental education, housing density, food security, and healthcare access. Nutritional status was assessed anthropometrically. Serum antibody titers against measles, diphtheria, and hepatitis B were measured using enzyme-linked immunosorbent assay (ELISA). Multivariate logistic regression was used to identify independent predictors of suboptimal immune response. Results: Among participants, 23.1% demonstrated suboptimal antibody titers to at least one antigen. Children from low-income households had significantly lower geometric mean titers (GMTs) for measles (1,245 ± 487 vs. 2,118 ± 612 mIU/mL; p < 0.001) and diphtheria (0.82 ± 0.34 vs. 1.47 ± 0.51 IU/mL; p < 0.001) compared to higher-income counterparts. Stunting (OR = 2.31; 95% CI: 1.42–3.76; p = 0.001), low maternal education (OR = 1.89; 95% CI: 1.18–3.02; p = 0.008), and food insecurity (OR = 2.14; 95% CI: 1.33–3.44; p = 0.002) were independent predictors of suboptimal immune response. Conclusion: Social determinants of health significantly influence immune responses to routine childhood vaccinations. Addressing socioeconomic inequities may enhance vaccination effectiveness and reduce disparities in vaccine-preventable disease burden.