This is a multicenter, double-blind, randomized, placebo-controlled field trial to evaluate the epidemiology of natural infection with ETEC occurring after transcutaneous immunization in a field setting.

The primary objectives of the study are to evaluate the incidence of ETEC illness in a field setting and to compare the safety of LT delivered by TCI with placebo. The secondary objectives include, but are not limited to:

evaluate the stool frequency per episode of ETEC illness in placebo recipients, to evaluate the immunogenicity of LT delivered by TCI, to evaluate the incidence of IBS following travel to areas of ETEC endemnicity, and to evaluate the incidence of VPO in placebo and LT patch recipients.

Inclusion Criteria:

• Healthy adult men and women 18-64 years of age inclusive at screening
• Signed Informed Consent form
• Planned travel to an area within 2 ½ hours traveling distance of Cuernavaca or Guadalajara, Mexico or Antigua, Guatemala (minimum stay of 7 days)
• If female who is not post-menopausal or surgically sterile, negative pregnancy test (within 24 hours prior to vaccination) and agreement to employ an effective form of birth control or practice abstinence through the end of the study.

Exclusion Criteria:

• Clinically significant abnormalities as determined by the Investigator/clinician during physical inspection
• Received investigational product from 30 days before date of first vaccination or during the entire study period
• Ever received LT, ETEC, or cholera vaccine
• History of traveler's diarrhea within the previous year
• Travel to a developing country within the last year
• Women who are pregnant or breastfeeding
• History of achlorhydria
• Evidence of immunosuppression, including concomitant immunosuppressive therapy; fever > 99.5°F (37.5°C) on day of vaccination
• Current problems with alcohol or substance abuse
• An employee of the study clinic
• Sensitivity or allergy to any of the vaccine components
• History of significant blood loss, blood product donation, or blood product recipient in the previous 60 days
• Planned use of Imodium or antibiotics for self treatment of diarrhea during the study period
• Visible tattoos or marks (tattoos/scars) at the vaccination areas that would prevent appropriate dermatologic monitoring of the vaccination sites; and
• Medical history of acute or chronic GI illness or major GI surgery.