Beyond Vaccine Coverage: The Neglected Treatment-Readiness Gap in Diphtheria Outbreak Response

Diphtheria has re‑emerged across the WHO African Region, with more than 20,000 suspected cases and over 1,200 deaths reported in 2025 alone. The conventional explanation centres on vaccine‑coverage gaps among zero‑dose and under‑immunized children. This narrative review argues that a second, less examined failure is equally responsible for outbreak mortality: the treatment pillar, timely access to diphtheria antitoxin (DAT), is structurally under‑supplied and is not measured by the same immunization surveillance systems that track vaccine coverage. We synthesised peer‑reviewed analyses of recent resurgences in Nigeria, Yemen and Haiti, individual case reports, and the published literature on DAT production, procurement and stockpiling (2022–2026), together with official outbreak communications. Three findings stand out. First, DAT supply depends on a small number of manufacturers and fragmented procurement, and no coordinating reserve comparable to the cholera vaccine stockpile exists. Second, case fatality is highest where DAT is unavailable, reported at 31% in a border district of Yemen, 25.8% in Guinea, and up to 40% in settings without access, even when vaccination gaps are comparable. Third, immunization information systems record vaccine doses but not district‑level antitoxin readiness. We propose that treatment readiness be made a standing indicator within the Expanded Programme on Immunization and integrated disease‑surveillance dashboards, and that a regional pooled reserve be established at the WHO‑recommended Dakar and Nairobi hubs. Closing the measurement asymmetry is a low‑cost, immediately actionable step to reduce diphtheria mortality. **Preprint statement**: This article is a preprint and has not been peer‑reviewed. It should not be used to guide clinical practice. Corresponding author: Yuran YANG, email:[email protected]