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Shigella Vaccine Prevents Illness in 31 of 34 Adults

7/21/2026

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Summary

Story summary

WRSs2 prevented shigellosis in 31 of 34 participants, versus 5 of 26 placebo recipients.
The trial enrolled 108 U.S. adults aged 18-49 who received 500,000-cell doses 28 days apart.
After challenge with ~1,500 live S. sonnei, 3 of 34 vaccinated got shigellosis versus 21 of 26 placebo.
Researchers will launch larger trials in three to six years that will include children, where S. flexneri dominates, since no vaccine is approved.

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Story summary

WRSs2 prevented shigellosis in 31 of 34 participants, versus 5 of 26 placebo recipients.
The trial enrolled 108 U.S. adults aged 18-49 who received 500,000-cell doses 28 days apart.
After challenge with ~1,500 live S. sonnei, 3 of 34 vaccinated got shigellosis versus 21 of 26 placebo.
Researchers will launch larger trials in three to six years that will include children, where S. flexneri dominates, since no vaccine is approved.