PLOS Medicine · 21 October 2026 · From issue 55
Analysis of the impact of naturally-acquired immunity on Shigella vaccine performance to inform clinical trials: A simulation-based modeling study
In computer simulations, most Shigella vaccine trial designs made the vaccine look weaker than it truly is.
Avnika B. Amin, Maria Garcia Quesada et al.
Children in places with lots of Shigella germs often build up natural protection from repeated infections. This can make unvaccinated kids look almost as protected as vaccinated kids in a trial. That makes the vaccine look weaker than it really is. Computer models tested six ways of running a Shigella vaccine trial. Only one method, which actively checks kids for infection and counts outcomes a simple way, gave accurate results every time. The other five methods underestimated how well the vaccine worked, by up to 20 percentage points, and the errors got worse in places with more disease.
How much five of six tested trial designs underestimated true vaccine protection against Shigella.
Simulation only, not a real trial, based on limited natural immunity data.
Integrity screen: passed (3 checks) Checked 30 October 2026. Retraction record: none. DOI resolves at doi.org. Metadata record found (PLOS Medicine). Read the source
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