Post-Campaign Evaluation of Diphtheria Vaccination Coverage in Somalia Following the 2025–2026 Outbreak Response

Background: Although a protective vaccine is available, diphtheria reemerged in Somalia starting in mid-2023 with outbreak reported throughout the country in 2025. In response, the Federal Ministry of Health (FMoH) developed a diphtheria outbreak response plan in 2025, launching a vaccination campaign with the first round conducted in 2025 and a second round in early 2026. The vaccination campaign was a mass public health push to rapidly deliver Pentavalent and Td vaccines to children in Somalia regardless of past vaccination status, to stop the diphtheria outbreak. During the campaign, under 5 children received Pentavalent vaccines, while 5-15 years olds received Diphtheria and Tetanus (Td). This study aims to evaluate the post-campaign coverage of diphtheria vaccines in the three most stable states in Somalia, namely the Benadir region, Puntland, and Galmudug states. Methods: The post-campaign coverage survey (PCCS) was conducted from May 18th to July 21st, 2026, in Benadir, Galmudug, and Puntland states. A two-stage cluster sampling design was employed, whereby 362 clusters were randomly selected from a national sampling frame covering all accessible districts, villages, and nomadic areas across the three states. The sample size was calculated according to the WHO 2018 manual, resulting in the selection of 120 clusters and 1,335 households from each state, culminating in a total of 4,093 interviews and covered 9184 children. Surveys were carried out by 152 trained personnel equipped with the KoboCollect app for digital data collection. Ethical approval was obtained from the Somali National University Ethical Committee. Results: Among the children, 49.7% were aged 0 to <5 years, and 50.3% were aged 5 to 15 years. Weighted data indicated that 84.1% of children aged 0 to 15 years across the three states received at least one dose of the diphtheria vaccine during the campaign (95% CI: 80.4% to 87.2%). Among those vaccinated, only 25% of children under 5 years of age and 36% of children aged 5 to 15 years received two doses. Vaccination coverage varied significantly by state: Puntland reported the highest coverage at 93.9%, while Galmudug had the lowest at 75.4% (95% CI: 69.2–80.7%), and Benadir showed intermediate coverage at 80.3% (95% CI: 74.5–85.1%). Geographically, internally displaced persons (IDPs) and nomadic populations had the lowest coverage rates, at 71.9% (95% CI: 55.0–84.2%) and 72.6% (95% CI: 57.9–83.7%) respectively. The primary reason for children not being vaccinated was a lack of awareness about the vaccination campaign. Conclusion: Post-campaign vaccination coverage is notably lower in Galmudug, the most fragile of the three states in terms of security. This indicates that even among Somalia’s relatively stable states, vaccination coverage tends to reflect the security situation of each state. Furthermore, despite the campaign has achieved a relatively high overall vaccination rate of 84.1% in the three states, specific groups—particularly nomadic populations and IDPs remain underserved. Efforts must be intensified to improve accessibility and ensure equitable and comprehensive vaccine coverage for all children throughout Somalia.