School-associated measles outbreak driven by vaccination gaps, sociocultural barriers, and delayed detection in Gomba...

On May 27, 2025 a measles outbreak was confirmed in Kabulasoke Subcounty, Gomba District, Uganda, following a suspected measles-related death. We investigated the outbreak to determine its magnitude, identify risk factors for transmission, estimate measles-rubella vaccination coverage (VC) and vaccine effectiveness (VE), and inform control measures.

We defined a suspected case as onset of fever and maculopapular rash plus ≥ 1 of cough, coryza, or conjunctivitis, in a Kabulasoke Subcounty resident during March-August, 2025; confirmed cases had measles-specific IgM antibodies. We compared exposures of 80 case-patients with 160 age- and sex-matched controls. Vaccination coverage was estimated as the proportion of vaccinated controls; VE was calculated as (1-aOR) *100%, using conditional logistic regression. Sociocultural factors were explored through 15 in-depth and key informant interviews, analysed by inductive thematic analysis.

We identified 106 cases (5 laboratory-confirmed, 1 death); overall attack rate (AR):2.4/1,000 population. Children aged 9-17 months were most affected (13/1,000), with clustering in infant school X. Response was initiated 33 days after detection. School attendance (aOR = 1.67; 95% CI: 1.05-2.71) and contact with symptomatic peers (aOR = 2.12; 95% CI: 1.21-3.70) were associated with infection, while vaccination was protective (aOR = 0.39; 95% CI: 0.27-0.55). Vaccination coverage was 72%, and VE was 60%. Qualitative findings revealed male-dominated decision-making, vaccine mistrust, and cultural framing of measles as a self-resolving illness as vaccination barriers.

This outbreak was driven by suboptimal vaccination coverage, school-based transmission, and delayed detection. Strengthening routine immunisation, integrating schools into outbreak prevention, and addressing sociocultural barriers are essential to prevent future outbreaks.