Vaccination of children in low-resource countries against Shigella is unlikely to present an undue risk of reactive arthritis

Shigellosis is a major cause of morbidity and mortality among children in low-resource countries. Promising vaccine strategies in development include genetically attenuated Shigella, killed whole cell vaccines, subcellular vaccines, and O-polysaccharide-protein conjugates. There is a concern that Shigella vaccines could either induce reactive arthritis or could prime vaccinees for arthritis after a subsequent exposure to the pathogen because shigellosis is associated with reactive arthritis, especially in patients expressing the HLA B27 histocompatibility antigen. Our understanding of the pathogenesis of reactive arthritis is incomplete, and even surrogate biomarkers of bacterial arthritogenic activity have not yet been identified. Nonetheless, all of the Shigella vaccine strategies currently in development are designed to limit inflammation and intracellular antigen persistence that could trigger arthritogenic sequelae. The relatively low occurrence of the HLA B27 phenotype in most Shigella endemic areas, and the rarity of reported reactive arthritis in these populations, suggests that vaccination with attenuated, killed, or subcellular vaccines may not increase the background incidence of arthritic sequelae. More importantly, incidence rates of shigellosis in children living in low-resource countries suggest that, during maturation, the entire pediatric population may be infected with Shigella-possibly with devastating consequences. Therefore, clinical trials of candidate Shigella vaccines should be pursued aggressively in the developing world, beginning with a Phase 1 in HLA B27-negative volunteers, but proceeding to Phase 2 and Phase 3 in unscreened volunteers. Post-vaccination monitoring for possible reactive arthritis should be included in all clinical protocols.