Projecting vaccination coverage and zero-dose children in urban populations to 2050: A modeling study

OBJECTIVES: Rapid urbanization is reshaping the distribution of unvaccinated children worldwide, with zero-dose children increasingly concentrated in urban poor settings. We quantified the implications of urbanization and intra-urban wealth stratification for vaccination coverage through 2050. METHODS: We modeled DTP1 (first dose of diphtheria-tetanus-pertussis vaccine) coverage and zero-dose children for Nigeria, India, Pakistan, Ethiopia, Indonesia, Angola, and Afghanistan and derived global estimates under three projection scenarios: continued historical progress (extrapolating 2000-2019 pre-pandemic trends), static percentage (2023 coverage rates held constant), and static absolute (2023 vaccinated counts held constant). Urban populations were stratified into poor and non-poor strata, using Demographic and Health Surveys-derived coverage ratios. RESULTS: By 2050, annual DTP1 zero-dose children in urban poor settings worldwide are projected at 1.1 million under continued historical progress (90% prediction interval for overall coverage: 96.9-97.4%), 5.0 million under static percentage, and 5.7 million under static absolute. Continued historical progress would avert 256.9 million cumulative DTP1 zero-dose child-years over 2023-2050 compared with static absolute. CONCLUSION: Maintaining current coverage rates is insufficient to prevent zero-dose numbers from rising in growing populations. Accelerating coverage gains-particularly, among urban poor communities-is necessary to meet Immunisation Agenda 2030 targets. These are illustrative scenarios; relative differences between scenarios are more robust than absolute estimates.