Epidemiology of Shigella sonnei and Shigella flexneri in the Global Pediatric Diarrhea Surveillance network, 2017-2022

Background Shigella is a leading cause of diarrhea in children in low- and middle-income countries (LMICs). Optimizing the impact of vaccines necessitates an accurate characterization of Shigella serotype prevalence. We describe the burden, epidemiology and characteristics of S. sonnei and S. flexneri diarrhea in the Global Pediatric Diarrhea Surveillance (GPDS) network. Methods GPDS is a World Health Organization-coordinated surveillance network investigating the etiology of hospitalized diarrhea among children aged <5 years. GPDS enrolls children hospitalized with diarrhea at 38 sentinel surveillance sites in 31 LMICs. Randomly selected stool specimens from these children were tested by quantitative polymerase chain reaction to detect a broad range of enteropathogens as well as to identify S. sonnei and S. flexneri serotypes. We estimated pathogen-specific attributable fractions and incidence of diarrheal hospitalizations. Results During 2017-2022, GPDS enrolled 70,750 children aged <5 years hospitalized with diarrhea, of which 16,458 (23.3%) were randomly selected for qPCR testing. Globally, Shigella caused 9.8% (95% Confidence Interval [CI]: 8.4, 11.3) of hospitalized diarrhea, with 28.3% of cases occurring in children aged {pound}12 months. The estimated attributable incidence of Shigella-associated diarrhea hospitalizations decreased from 1.27 (95% CI: 0.95, 1.64) per 1,000 child years in 2017-2018 to 0.88 (0.67, 1.10) in 2021-2022. Among typeable Shigella cases, 34.8% were S. sonnei, 24.2% were S. flexneri 2a, and 9.9% were S. flexneri 1b. Vaccines currently in development would cover an estimated 59.0% to 72.2% of cases. Conclusions These findings support the role of Shigella as an important cause of the most severe diarrhea in young children. The breadth of homotypic protection provided by Shigella vaccines in clinical development varied by region, and these broadly representative data can aid in prioritization. Non-dysenteric Shigella could not be readily differentiated from other causes of hospitalized diarrhea based on clinical characteristics.