IJID regions · 2026
Timeliness of childhood vaccination in Iran: Survival analysis of a national immunization survey, 2019.
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Izadi Shahrokh, Mansourian Marjan, Zahraei Seyed Mohsen, Seddiq Sahar
Аннотация
OBJECTIVES: Despite high vaccination coverage in Iran, delays in administering age-appropriate vaccines may compromise overall protection. This study used survival analysis to examine the timeliness of vaccine delivery and its sociodemographic correlates.
METHODS: We analyzed the vaccination histories of 8248 children aged 24-35 months from the 2019 National Immunization Coverage Survey. Timeliness for the third pentavalent dose (Penta3) and the first measles-mumps-rubella dose (MMR1) was assessed via Kaplan-Meier curves and Cox proportional hazards models, with time-dependent effects where the proportionality assumption was violated. The Gini index was accounted for through stratification.
RESULTS: Although Penta3 coverage was high at 99.13%, only 72.23% of participants had received their vaccinations within the recommended time frame (P < 0.001). In contrast, the disparity between total coverage (99.04%) and valid coverage (94.36%) for MMR1 was notably less pronounced (P = 0.003). For Penta3, maternal literacy was associated with higher on-time vaccination (hazard ratio [HR] = 1.38; 95% confidence interval [CI] = 1.16-1.66), whereas a birth order ≥4 was associated with lower timeliness (HR = 0.72; 0.63-0.82). For MMR1, urban residence was associated with a lower baseline hazard of on-time vaccination (HR = 0.57; 0.49-0.67), alongside a modest increase in the time-dependent HR (TD-HR = 1.02; 1.01-1.03), suggesting partial convergence over time. Maternal literacy showed no strong main effect for MMR1 (HR = 0.94; 0.64-1.37), with a slight positive time trend (TD-HR = 1.01; 0.99-1.04).
CONCLUSION: Even with high coverage, gaps in on-time vaccination remain-particularly, among higher-parity children and in urban settings at baseline. The findings underscore the value of routinely reporting timeliness (not just total coverage) and of targeting context-specific barriers (e.g. for large families and urban clinics) to narrow disparities in on-time immunization.
METHODS: We analyzed the vaccination histories of 8248 children aged 24-35 months from the 2019 National Immunization Coverage Survey. Timeliness for the third pentavalent dose (Penta3) and the first measles-mumps-rubella dose (MMR1) was assessed via Kaplan-Meier curves and Cox proportional hazards models, with time-dependent effects where the proportionality assumption was violated. The Gini index was accounted for through stratification.
RESULTS: Although Penta3 coverage was high at 99.13%, only 72.23% of participants had received their vaccinations within the recommended time frame (P < 0.001). In contrast, the disparity between total coverage (99.04%) and valid coverage (94.36%) for MMR1 was notably less pronounced (P = 0.003). For Penta3, maternal literacy was associated with higher on-time vaccination (hazard ratio [HR] = 1.38; 95% confidence interval [CI] = 1.16-1.66), whereas a birth order ≥4 was associated with lower timeliness (HR = 0.72; 0.63-0.82). For MMR1, urban residence was associated with a lower baseline hazard of on-time vaccination (HR = 0.57; 0.49-0.67), alongside a modest increase in the time-dependent HR (TD-HR = 1.02; 1.01-1.03), suggesting partial convergence over time. Maternal literacy showed no strong main effect for MMR1 (HR = 0.94; 0.64-1.37), with a slight positive time trend (TD-HR = 1.01; 0.99-1.04).
CONCLUSION: Even with high coverage, gaps in on-time vaccination remain-particularly, among higher-parity children and in urban settings at baseline. The findings underscore the value of routinely reporting timeliness (not just total coverage) and of targeting context-specific barriers (e.g. for large families and urban clinics) to narrow disparities in on-time immunization.