Burden of Shigella among children with diarrhea in the Americas: A systematic review and meta-analysis

Introduction Shigella is a leading cause of diarrhea worldwide. While the burden of Shigella has been shown to be highest in Africa and Asia, recent studies have also shown considerable burden in the Americas. With several pediatric Shigella vaccines in clinical development, policymakers in the region will eventually consider whether a Shigella vaccine is appropriate for their setting. Methods We conducted a systematic review and meta-analyses to summarize the burden (characterized by prevalence, incidence, and attributable fraction estimates) of Shigella diarrhea among children under 72 months in the Americas, excluding the U.S., Canada, and Greenland. We searched published and pre-print articles available in six databases from January 1, 2000 through July 18, 2024. Random effects meta-analyses were conducted for subgroups of interest when relevant data from at least two studies were present. Results This review included 34 studies conducted across 14 countries in the region. Prevalence was most frequently reported, followed by incidence, then attributable fraction. Across all prevalence studies that used a culture detection method (n = 23), the pooled prevalence of Shigella among diarrhea cases was 3.1% (95% CI: 1.6-5.8). The pooled prevalence among 7 studies that used PCR/qPCR detection methods was 16.5% (95% CI: 11.1-24.0). Among culture-based results, the pooled prevalence estimate for children <12 months was 1.0% (95% CI: 0.1 – 7.7) compared to 4.6% (95% CI: 1.2 – 15.4) for children ≥12 months. Conclusion Despite varying reporting practices, we found Shigella to be an important contributor to diarrhea in many settings in the Americas with substantial heterogeneity. Limited geographic representation and variable reporting of age group specific estimates were the major gaps in data. Investment in Shigella surveillance in the Americas using a standardized methodology can contribute to accelerating Shigella vaccine development in consideration of regional preferences and optimal age of introduction.