Diphtheria, caused by toxigenic Corynebacterium diphtheriae, was once a leading cause of childhood morbidity and mortality worldwide. The development of diphtheria antitoxin and toxoid vaccination resulted in dramatic reductions in global disease burden. Despite significant success, diphtheria persists in regions with low immunization coverage, fragile healthcare infrastructure, and waning adult immunity. This review summarizes epidemiologic trends from 1922 to 2025, examines the impact of vaccination efforts in the United States and worldwide, highlights historical outbreaks including the 1990s epidemic in the former Soviet republics, and discusses clinical features, diagnostics, treatment, and current preparedness. Continued robust immunization programs remain essential for sustained control.
Kobaidze et al. (2026) studied this question.