VXA-NVV-103 is a phase 1B Randomized, Double-Blind, Placebo-Controlled, Multi-Center Safety and Immunogenicity Study of Adenoviral-vector Based Oral Norovirus Vaccines Expressing GI.1 or GII.4 VP1 with Monovalent or Bivalent Dosing in Healthy Adult Volunteers. The study consists of 2 parts: Part 1 is the double-blinded portion where subjects will be randomized to one of two monovalent vaccine groups, bivalent vaccine group or placebo. Subjects will be followed for ~4 weeks post vaccination for safety and immunogenicity. Part 2 will consist of an open label booster vaccination for the bivalent treatment group ~4 months post initial vaccination. All subjects will be followed for long term safety for 1 year post initial vaccination.

VXA-NVV-103 is a phase 1B Randomized, Double-Blind, Placebo-Controlled, Multi-Center Safety and Immunogenicity Study of Adenoviral-vector Based Oral Norovirus Vaccines Expressing GI.1 or GII.4 VP1 with Monovalent or Bivalent Dosing in Healthy Adult Volunteers. The study consists of 2 parts with will enroll 86 subjects:

Part 1 - Double Blind Period: Post confirmation of eligibility subjects will be randomized in a double-blinded manner to one of four treatment arms. Treatment Group 1 will contain an open-label sentinel group of 6 subjects to be enrolled prior to initiation of subsequent treatment groups. After review of the safety data and confirmation the dose is well tolerated through Study Day 8, the rest of the study will proceed in a double-blinded, randomized fashion. The 6 sentinel subjects will not be part of the 16 subjects in Treatment Group 1 to be enrolled in the double-blinded placebo-controlled cohort; randomization will be 1:1:2:1 for Treatment Groups 1 through 4 respectively.

Study Design and Vaccine Groups

1. Monovalent GII.4 VXA-G2.4-NS (6 sentinels / 16 randomized)
2. Monovalent GI.1 VXA-G1.1-NN (16 randomized)
3. Bivalent GII.4/GI.1 VXA-G2.4-NS + VXA-G1.1-NN (32 randomized)
4. Placebo Tablets no vaccine (16 randomized)

Subjects will be followed for ~4 weeks post vaccination for safety and immunogenicity. The study database will be locked post completion of Day 29 visits.

Part 2 will consist of an open label booster vaccination for the bivalent treatment group ~4 months post initial vaccination. Subjects will be followed for safety and immunogenicity for ~4 weeks post the boost.

All subjects will be followed for long term safety for 1 year post initial vaccination.

Inclusion Criteria:

• Male or female between the ages of 18 to 49 years, inclusive
• General good health, without significant medical illness, based on medical history, physical examination, vital signs, and clinical laboratories
• Demonstrate comprehension of the protocol procedures and willingness to adhere to all visits and assessments
• Body mass index between 17 and 35 at screening
• Female subjects must have a negative pregnancy test at screening and before each vaccination and fulfill protocol specified criteria for adequate birth control.

Exclusion Criteria:

• Presence of a significant medical condition which in the opinion of the investigator precludes participation in the study
• History of cancer or cancer treatment within past 3 years
• Presence of immunosuppression or medical condition possibly associated with impaired immune responsiveness, including diabetes mellitus or angioedema
• Donation or use of blood/blood products within 4 weeks prior to vaccination
• Diagnosed bleeding disorder or significant bruising or bleeding difficulties that could make blood draws problematic.
• Any condition that resulted in the absence or removal of the spleen
• Positive HIV, HBsAg or HCV tests at the screening visit
• Use of antibiotics, proton pump inhibitors, H2 blockers or antacids within 7 days of vaccination
• Use of medications known to affect the immune function within 14 days of vaccination
• Use of NSAIDs, sulfonylureas, and angiotensin II blockers within 7 days of vaccination
• Evidence of recent or of current nonbacterial gastroenteritis suggestive of NV infection to any gastroenteritis within 2 weeks of vaccination
• History of drug, alcohol or chemical abuse within 1 year of screening or positive urine drug test at screening
• Consistent/habitual smoking within 2 months as per medical history
• History of hypersensitivity or allergic reaction to any component of the investigational vaccine or placebo
• Use of any investigational vaccine, drug or device within 8 weeks preceding vaccination, or planned use of the above stated for the duration of the study

Study results will be summarized and presented by treatment arm comparisons. Individual subject data will not be shared with other researchers.

Study subjects, study site and study team will remain blinded to treatment during study period 1 (initial vaccination through Day 29 visits and subsequent database lock)