Epidemiology of Rubella Virus in a Fragile and Conflict-affected Setting - A Retrospective Analysis of 11 Years Case-based Data in South Sudan.

INTRODUCTION

Since establishing routine immunization services in what was then known as Sudan in 1974, South Sudan has not yet introduced the rubella-containing vaccine into its national immunization schedule. This study aims to assess the burden of rubella infection within the existing measles case-based surveillance framework to provide evidence supporting advocacy for introducing the rubella-containing vaccine into the national immunization program.

METHODS

This study conducted a retrospective descriptive analysis of rubella infection using measles case-based surveillance data from 2013 to 2023. Data were analyzed with descriptive statistics and logistic regression using Epi Info, version 7.

RESULTS

During the study period, 17,987 suspected measles cases were reported, with 4944 serum samples collected. Of these, 2083 (42.1%) were positive for measles immunoglobulin M antibodies. Among 2861 samples that tested negative or indeterminate for measles, 678 (23.7%) tested positive for rubella immunoglobulin M antibodies. The study observed a significant increase in rubella positivity rates from 1.6% in 2014 to 34.4% in 2020. Logistic regression analysis showed that rubella infection was significantly more likely among children aged 5-9 years (odds ratio [OR] = 2.234; 95% confidence interval [CI]; 1.468-3.473, < .001), 10-14 years (OR = 2.101; 95% CI, 1.570-4.428; < .001), and 1-4 years (OR = 1.733; 95% CI, 1.149-2.687; = .003), compared to children aged younger than 1 year (reference group). Rubella positivity was also slightly higher in urban settings than rural areas (OR = 1.139; 95% CI, 1.004-1.527; = .034). Rubella cases demonstrated clear seasonality, with increased cases occurring from December and peaking in March.

CONCLUSIONS

The study identified a high prevalence of rubella among young children, particularly those aged 1-9 years and in urban areas, highlighting the need for targeted vaccination strategies. These findings strongly support introducing the rubella vaccine into the national immunization program.