Outcomes of home-based versus facility-based care for mild diphtheria during a large epidemic in Kano State, Nigeria: a retrospective matched cohort study

Background During Nigeria's largest recorded diphtheria outbreak, hospital capacity in Kano State was rapidly overwhelmed. Medecins Sans Frontieres introduced home-based care (HBC) for patients with mild disease to prioritise facility-based care for severe cases. We assessed whether HBC was non-inferior to facility-based treatment in terms of mortality, sequelae, and household transmission. Methods We conducted a retrospective matched cohort study. Mild diphtheria cases treated between January 2023 and May 2024 were matched 1:1 by treatment modality (HBC or diphtheria treatment centre [DTC]) on sex, age group, vaccination status, and residence. Conditional logistic regression estimated the association between treatment modality and mortality, with robustness assessed through propensity score weighting, sensitivity analyses, and E-value computation. Findings Of 990 sampled patients, 678 (367 HBC, 311 DTC) were enrolled (68.5%). After adjustment, treatment modality was not independently associated with mortality (HBC vs. DTC: aOR 0.40, 95% CI 0.13-1.30), with similar estimates across sensitivity analyses (E-value 4.40). Clinical complications were the strongest predictor of death (aOR 23.1, 95% CI 1.73-307). Vaccination was protective (aOR 0.28, 95% CI 0.08-0.94) and treatment delay of four or more days increased mortality (aOR 4.15, 95% CI 1.23-14.0). HBC was not associated with increased household transmission or long-term sequelae. Interpretation Vaccination and early treatment, rather than care setting, were the main determinants of survival. When supported by clinical triage and structured follow-up, decentralised care can be used to manage mild cases during diphtheria epidemics in settings with constrained hospital capacity.