BMC Infect Dis

BackgroundIn April 2015, Kamwenge District, western Uganda reported a measles outbreak. We investigated the outbreak to identify potential exposures that facilitated measles transmission, assess vaccine effectiveness (VE) and vaccination coverage (VC), and recommend prevention and control measures.MethodsFor this investigation, a probable case was defined as onset of fever and generalized maculopapular rash, plus 651 of the following symptoms: Coryza, conjunctivitis, or cough. A confirmed case was defined as a probable case plus identification of measles-specific IgM in serum. For case-finding, we reviewed patients\u2019 medical records and conducted in-home patient examination. In a case-control study, we compared exposures of case-patients and controls matched by age and village of residence. For children aged 9\ua0m-5y, we estimated VC using the percent of children among the controls who had been vaccinated against measles, and calculated VE using the formula, VE\u2009=\u20091 - ORM-H, where ORM-H was the Mantel-Haenszel odds ratio associated with having a measles vaccination history.ResultsWe identified 213 probable cases with onset between April and August, 2015. Of 23 blood specimens collected, 78% were positive for measles-specific IgM. Measles attack rate was highest in the youngest age-group, 0-5y (13/10,000), and decreased as age increased. The epidemic curve indicated sustained propagation in the community. Of the 50 case-patients and 200 controls, 42% of case-patients and 12% of controls visited health centers during their likely exposure period (ORM-H\u2009=\u20096.1; 95% CI\u2009=\u20092.7\u201314). Among children aged 9\ua0m-5y, VE was estimated at 70% (95% CI: 24\u201388%), and VC at 75% (95% CI: 67\u201383%). Excessive crowding was observed at all health centers; no patient triage-system existed.ConclusionsThe spread of measles during this outbreak was facilitated by patient mixing at crowded health centers, suboptimal VE and inadequate VC. We recommended emergency immunization campaign targeting children