The study, published in The Lancet Infectious Diseases, marks a significant milestone in a century-long effort to combat the pathogen. Shigella infects tens of millions globally each year, proving particularly lethal to children between one and five years old. In the United States alone, the bacteria causes approximately 450,000 infections annually. As antibiotic resistance complicates traditional treatment, the need for a preventive measure has become critical.

Dr. Robert Frenck, director of the Vaccine Research Center at Cincinnati Children's and a joint senior author, oversaw the phase 2 trial involving 108 healthy adults. Participants receiving two doses of the live-attenuated vaccine demonstrated not only higher protection rates compared to the placebo group but also reduced symptom severity and lower bacterial shedding. While the results support moving the candidate into larger trials, including those in endemic regions, researchers are currently refining dosing protocols to address minor side effects observed during the initial study. The development remains a collaborative effort involving the National Institutes of Health, the U.S. Department of Defense, and various academic institutions.