Safety and Efficacy Study of a Vaccine Against Enterotoxigenic Escherichia Coli (ETEC) to Prevent Moderate to Severe Diarrhea

This is a research study about an experimental (investigational) vaccine called ACE527. ACE527 is a vaccine that is being made to prevent disease from a germ called enterotoxigenic Escherichia coli (ETEC). This germ causes diarrhea, largely in children living in developing countries and in travelers to those countries. One purpose of this study is to see if the vaccine is safe and develops an immune response. Another purpose is to see if it prevents people from getting sick when exposed to the ETEC germ. This ETEC germ is also experimental (investigational).