Safety, and Efficacy Study of ShigETEC, a Live, Attenuated, Oral Combination Vaccine to Prevent Shigella and ETEC Disease Delivered to Healthy Adults Ages 18 to 50 Years Old

The ShigETEC vaccine will be administered orally 4 times at 3-day intervals as a bacterial suspension in a volume of 30 mL per dose (target to contain 5x10\^10 CFU)

Eligible participants will be randomly assigned in a 1:1 ratio to receive either ShigETEC 5x10\^10 colony forming units (CFU) or placebo. Participants will receive their assigned treatment on Days 1, 4, 7, and 10.

In the challenge stage all participants will receive 1 oral dose of Shigella flexneri 2457T at a dose of 1.5x10\^3 CFU.