Factors associated with measles infection during the 2025-6 outbreak in Burao, Somaliland: a case-control study

Somaliland has recurrent measles transmission, but outbreak-specific evidence on modifiable child, household, and health-service factors is limited. We examined factors associated with measles case status during the 2025-6 Burao outbreak.

We conducted a community-based unmatched case-control study among children aged <15 years from 14 June to 8 July 2026. Cases were enrolled consecutively and controls sampled systematically from households using a random start and every fourth household. Cluster-robust logistic regression estimated adjusted ORs (aORs), with indeterminate responses modeled separately.

Among 804 children (290 cases, 514 controls), case status was associated with non-vaccination (aOR 2.12, 95% CI 1.02-4.42), close contact (3.00, 1.72-5.25), reported health-facility attendance (2.79, 1.91-4.06), vaccine unavailability (2.62, 1.17-5.85), and trucked/vendor water (2.98, 2.03-4.36). Prior malnutrition, large-gathering attendance, household vaccination-refusal history, and poor ventilation were also associated. Health-facility attendance referred to the 21 days before rash onset/reference date, but exact visit dates were not collected.

Measles case status was associated with immunity gaps, contact, household conditions, and service-related factors. Response priorities include reliable vaccine availability, catch-up vaccination, and contact-based action. The health-facility attendance association is temporally ambiguous and does not establish healthcare-associated transmission.