A Phase 1, Randomized, Double-Blind, Placebo-Controlled, Dose-Ranging Trial to Determine the Safety and Immunogenicity of an Adenoviral-Vector Based Respiratory Syncytial Virus (RSV) F Protein Vaccine (VXA-RSV-f) Expressing Protein F and dsRNA Adjuvant Administered Orally to Healthy Volunteers

The study will enroll 66 subjects in four cohorts. All subjects will receive a single administration of VXA-RSV-f at a low dose, a high dose or placebo.

Two sentinel groups will enroll 3 subjects each in an open-label manner (Cohorts 1 and 3) to receive VXA-RSV-f prior to enrolling either of the randomized, controlled cohorts (Cohorts 2 and 4). Within the double-blinded Cohorts (2 and 4), placebo subjects will receive the same number of tablets as the vaccine subjects in that Cohort. Subjects will be enrolled and dosed in the low dose groups prior to initiation of dosing in the high dose group.

Cohort 1: 3 subjects at low dose Cohort 2: 20 subjects at low dose and 10 placebo Cohort 3: 3 subjects at high dose Cohort 4: 20 subjects at low dose and 10 placebo

Subjects will be followed for 28 days post vaccination for preliminary immunogenicity. Subjects will continue to be followed for 1 year post-vaccination for long term safety.

Inclusion Criteria:

1. Male or female volunteers aged 18 - 49 years, inclusive
2. Able to give written informed consent
3. Healthy (no clinically significant health concerns)
4. Safety laboratory values within the following range criteria normal range
5. Body mass index between 17 and 35 at screening

Exclusion Criteria:

1. Receipt of any investigational RSV vaccine within two years prior to study
2. Receipt of any investigational vaccine, drug or device within 8 weeks preceding vaccination
3. Administration of any licensed vaccine within 30 days prior to study
4. Presence of significant uncontrolled medical or psychiatric illness (acute or chronic) including institution of new medical/surgical treatment or significant dose alteration for uncontrolled symptoms or drug toxicity within 3 months of screening and reconfirmed at baseline
5. History of drug, alcohol or chemical abuse within 1 year prior to vaccination
6. Presence of a fever ≥ 38oC measured orally at baseline
7. Stool sample with occult blood at screening

Data may be made available to subjects following the 1 year safety follow-up period.