Last mile at the center of immunization delivery.

While advances in immunization led to major reductions in vaccine-preventable diseases in the past four decades, large gaps remain in the delivery of immunization services. In this perspective, we use illustrative examples to discuss gaps in global immunization and outline opportunities for evidence generation and intervention design to transform the last mile delivery of immunization services in global health. To address last mile gaps, technical limitations in global health surveillance infrastructure that result in imprecise estimates and overlapping obstacles that complicate immunization service delivery for selected groups need to be addressed. Additionally, leveraging pro-equity strategies from the community level to the global level and across phases of translational health research could accelerate the equitable impact of immunization innovations on population health outcomes.