Protracted measles outbreak in a refugee-hosting setting in Kamwenge District, Uganda, 2025

Measles outbreaks continue to occur in Uganda despite measles-rubella (MR) vaccination. On 24 June 2025, Kamwenge District, a refugee-hosting area, reported three laboratory-confirmed measles cases. We investigated the outbreak to determine its magnitude, identify risk factors, and estimate vaccine effectiveness (VE), and vaccination coverage (VC). A suspected case was fever and generalized maculopapular rash with ≥ 1 of cough, coryza, or conjunctivitis among Kamwenge residents from 1 February to 7 July 2025; a confirmed case had measles-specific IgM. Cases were identified through health-facility records and community searches. We calculated attack rates (AR), conducted environmental assessments, and performed an age-matched case-control study using neighborhood controls. Conditional logistic regression estimated adjusted odds ratios (aORs). VE was calculated as (1−OR_ M−H )×100; VC was the proportion of vaccinated eligible controls. We identified 109 cases (3 confirmed, 106 suspected); no deaths occurred. Of the cases, 48.6% were refugees. Overall AR was 3.2/10,000, highest among children aged 9–17 months (30.8/10,000) and refugees (13.3/10,000). Among 73 cases and 167 controls, attending a place of worship was associated with infection (aOR = 11.1; 95% CI 3.5–35.1), while MR1 (aOR = 0.3; 95% CI 0.1–0.7) and MR2 (aOR = 0.05; 95% CI 0.01–0.3) were protective. VE was 93% for MR1 and 95% for MR2. Coverage among eligible controls was 67% for MR1 and 36% for MR2. A prolonged outbreak occurred amid low MR coverage and high-contact social mixing. Strengthening routine two-dose vaccination, targeted vaccination in refugee-hosting communities, and prompt isolation of suspected cases may help prevent future outbreaks.