A Case-control Study Undertaken to Investigate a Rubella Outbreak in Lideta Sub City Woreda-3 Addis Ababa, Ethiopia

Objective: Rubella is a vaccine-preventable disease that is primarily unnoticed public health problem. Hence, this study aims to describe the outbreak in terms of person, place, time, guide control measures and determine risk factors associated in Lideta Sub City, Woreda-3, Addis Ababa, Ethiopia. Methods: A 1:2 unmatched case-control study was conducted from February 20, 2022, to June 10, 2022. Each rubella case was identified based on the World Health Organization standard case definition. A total of 32 cases and 64 controls were interviewed by using a structured questionnaire, then, bivariate analysis was conducted to prepare for further multivariate analysis to control all potential confounders to identify the true predictors of rubella infection, variables with a p-value <0.05 had a statistically significant association with rubella infection. Results: In the study setting, 32 rubella cases were listed in the line list and tested to laboratory confirmation. Based on the laboratory results, 1 case were inconclusive, while 11 cases laboratory tested positive for rubella IgM, with an attack rate of 2 per 1000. The current study showed that 59.4% of cases are female. In the multivariable analysis, ages between 1-2 years (AOR: 5.05, 95% CI: 1.49-17.12), undernourished children (AOR: 4.27, 95% CI: 1.38-13.17), travel history (AOR: 3.96, 95% CI: 1.34-11.76) and poor housing conditions (AOR: 4.18, 95% CI: 1.39-12.55) were significant factors associated with rubella infection. Conclusion: The outbreak was caused by the absence of a rubella surveillance system, and unvaccination against rubella which increased the transmission of rubella infection. Hence, immediate isolate and treat the sick person, functional rubella surveillance system, routine rubella vaccination for susceptible childbearing women, vaccination of infants, or a combined strategy could prevent similar outbreaks.