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CompletedNCT05626803Updated Apr 15, 2025Results posted

A Study to Determine the Safety and Immunogenicity of Bivalent GI.1 and GII.4 Vaccines in Healthy Volunteers

A Phase 2 interventional study of Open label Bivalent GII.4/GI.1 high dose vaccine 2×10 to the power 11 IU/dose and Bivalent GII.4/GI.1 high dose vaccine 2×10 to the power 11 IU/dose in Norovirus Infections, sponsored by Vaxart. Completed at 3 sites in United States. Open to participants aged 18 Years to 80 Years, including healthy volunteers. Per ClinicalTrials.gov, last updated 2025-04-15.

Sponsored by Vaxart · Phase 2, Interventional, and Prevention

Phase
Phase 2
Study type
Interventional
Enrollment
135
Allocation
Randomized
Ages
18 Years to 80 Years
Sex
All
01

Study summary

This study is designed to evaluate the safety and immunogenicity of two monovalent Norovirus (NoV) oral tableted vaccine candidates, VXA-G1.1-NN and VXA-GII.4-NS co-administered (bivalent delivery) against a matching placebo arm. Bivalent GI.1 and GII.4 vaccines are being investigated for the prevention of noroviral gastroenteritis caused by norovirus GI.1 and GII.4.

Read the detailed description

Norovirus infections are a leading cause of sporadic and epidemic gastroenteritis across all age groups worldwide. This study is designed as a standard double-blind placebo-controlled single administration, dose ranging study to evaluate the safety and immunogenicity of 2 different doses of VXA-GII.4-NS plus VXA-G1.1-NN (high and medium dose administered orally for the prevention of Norovirus infection), compared with a placebo.

This study will enroll a total of 135 subjects with10 sentinel subjects in an open label period (dosing staggered to not-more-than 2 subjects per 24 hours) and randomize 125 subjects in three arms.

The first 10 sentinel subjects will receive the open label high dose of active vaccine. If no dose-related toxicities are observed, and upon the recommendation of the SMC following review of safety data, subjects will be randomized in a 2:2:1 ratio to one of the 3 study arms to receive active vaccine or placebo. After vaccination on Day 1, the study will include an Active Study Period that runs through 4 weeks after administration (Day 29), and a Follow-up Period of one year for safety and duration of immune response.

02

Conditions studied

  • Norovirus Infections
03

In context

Caliciviridae Infections

22 studies on the registry are indexed under Caliciviridae Infections; 2 are open to participants now.

This study's enrollment of 135 is above the median of 63 across 20 interventional studies indexed under Caliciviridae Infections.

Browse Caliciviridae Infections studies →

Lead sponsor

Vaxart is the lead sponsor of 23 studies on the registry; none are open to participants now.

Of its 14 completed or terminated interventional studies of FDA-regulated products, 6 (43%) have results posted.

Counted across the registry records on this site, refreshed daily.

04

Who can participate

Ages eligible
18 Years to 80 Years
Sexes eligible
All
Accepts healthy volunteers
Yes

Eligibility criteria

Key Inclusion Criteria:

To be eligible for this study, subjects must meet all the following:

  1. In stable and good general health, without significant medical illness, based on medical history, physical examination, and vital signs at screening based on investigator judgement.
  2. Body mass index (BMI) between >/= 17.0 and \</= 35.0 kg/m2 at screening SNG.
  3. Available for all planned visits and tele-health appointment, and willing to complete all protocol-defined procedures and assessments (including ability and willingness to swallow multiple small enteric-coated tablets per study dose).
  4. Female subjects must not be breastfeeding and must provide a negative pregnancy test at screening and pre-dose.

  5. Female subjects must fulfill one of the following criteria:

    i. At least 1 year post-menopausal (defined as amenorrhea for greater than or equal to 12 consecutive months prior to screening without alternative medical cause) or surgically sterile.

    ii. Female subjects of childbearing potential must be willing to use a highly effective form of contraception for 30 days prior to initial vaccination and until 60 days after last vaccination. Acceptable forms are oral, implantable, intrauterine, transdermal, intravaginal, injectable, double barrier or abstinence (subjects using diaphragms must also use condom). The form of contraception must be approved by the investigator.

    iii. Male subjects must agree to practice abstinence from heterosexual intercourse or to use an effective method of birth control as noted above from first vaccination to 60 days after last vaccination. Male subjects must agree to refrain from donating sperm and practice abstinence from all intercourse or to use an effective method of double barrier birth control or condom as noted above from first vaccination to 60 days after last vaccination.

  6. Capable of understanding and giving signed informed consent which includes compliance with the requirements and restrictions listed in the ICF and in the protocol.

Key Exclusion Criteria:

The subjects must be excluded from participating in the study if they meet any of the following:

  1. Known clotting/bleeding issues and/or personal and family history with increased risk of bleeding or clotting.
  2. 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 prior to screening and reconfirmed at baseline.
  3. Cancer, or treatment for cancer or any procedure or preventive medication for cancer or to prevent recurrence, within past 3 years (excluding fully treated and resolved basal cell carcinoma or squamous cell carcinoma)
  4. Presence of immunosuppression or medical condition possibly associated with impaired immune responsiveness, including diabetes mellitus- type 1 and 2

  5. History of irritable bowel disease or other inflammatory digestive or gastrointestinal condition that could affect the distribution/safety evaluation of an orally administered vaccine targeting the mucosa of the small intestine. Such conditions may include but are not limited to:

    a. Any history of: i. GI malignancy ii. malabsorption iii. pancreatobiliary disorders iv. inflammatory bowel disease v. irritable bowel disease vi. hiatal hernia vii. surgical resection b. History of diagnosis or treatment in past 5 years of: i. esophageal or gastric motility disorder ii. gastro esophageal reflux disorder iii. peptic ulcer iv. cholecystectomy

  6. History of any form of angioedema
  7. History of serious reactions to vaccination such as anaphylaxis, respiratory problems, hives or abdominal pain
  8. Diagnosed bleeding disorder or significant bruising or bleeding difficulties that could make blood draws problematic.
  9. Any condition that resulted in the absence or removal of the spleen
  10. Acute disease within 72 hours prior to vaccination defined as the presence of a moderate or severe illness (as determined by the investigator through medical history and physical exam). (Assessment may be repeated once during Screening Period)
  11. Presence of a fever greater than or equal to 38°C measured orally at baseline.
  12. Any significant hospitalization within the last year which in the opinion of the investigator or sponsor could interfere with study participation.

  13. Any history or conditions that may lead to higher risk of clotting events and/or thrombocytopenia:

    1. Family or personal history of bleeding or thrombosis.
    2. History of heparin-related thrombotic events, and/or receiving heparin treatments.
    3. History of autoimmune or inflammatory disease.
    4. Presence of any of the following conditions known to increase risk of thrombosis within 6 months prior to screening:

    i. Recent surgery other than removal/biopsy of cutaneous lesions ii. Immobility (confined to bed or wheelchair for 3 or more successive days) iii. Head trauma with loss of consciousness or documented brain injury iv. Receipt of anticoagulants for prophylaxis of thrombosis v. Recent clinically significant infection, including hospitalization for COVID-19 infection.

  14. Any other condition that in the clinical judgement of the investigator would jeopardize the safety or rights of a subject taking the study drug, would render the subject unable to comply within the protocol or would interfere with the evaluation of the study endpoints diagnostic assessments.
  15. Positive human immunodeficiency virus (HIV), Hepatitis B surface antigen (HBsAg) or Hepatitis C virus (HCV) tests at the screening visit.
  16. History of GI bleeding including hematochezia (blood in stool) or melena (black stool)
  17. Positive urine drug screen for drugs of abuse at screening (positive test for marijuana is not exclusionary; however concurrent use of marijuana during the study Active period through Day 29 is prohibited).
  18. Positive breath or urine alcohol test at screening and baseline.
  19. Receipt of a licensed vaccine (including any COVID-19 vaccines under emergency use authorization) within 14 days prior to baseline vaccination or planned administration during the study active period (Day 29).
  20. Use of antibiotics, proton pump inhibitors, H2 blockers or antacids within 7 days prior to study drug administration or planned use during the active study period (Day 29).
  21. Use of medications known to affect the immune function (e.g., including but not limited to systemic corticosteroids, leukotriene modifiers, and JAK inhibitors) within 2 weeks before study drug administration or planned use during the active study period (Day 29).
  22. Daily use of nonsteroidal anti-inflammatory drugs within 7 days prior to study drug administration or planned use during the active study period (Day 29). Low dose daily ASA less than or equal to 100 mg for cardio-protection is not exclusionary.
  23. Administration of any investigational vaccine, drug or device within 8 weeks preceding study drug administration, or planned use within the duration of the study
  24. Previous participation in a Vaxart Clinical Trial or other NoV vaccine trial unless confirmed receipt of placebo.
  25. Donation or use of blood or blood products within 30 days prior to study drug administration or planned donation during the active study period (Day 29).
  26. History of drug, alcohol, or chemical abuse within 1 year of screening.
  27. History of hypersensitivity or allergic reaction to any component of the investigational vaccine, including but not limited to fish gelatin allergy.
05

Study design

Phase
Phase 2
Primary purpose
Prevention
Allocation
Randomized
Intervention model
Parallel assignment
Masking
Quadruple (Participant, Care provider, Investigator, Outcomes assessor)
Enrollment
135 participants (actual)

Study arms

  • Experimental
    Open Label Sentinel

    Bivalent GII.4/GI.1 vaccine Bivalent GII.4/GI.1 high dose vaccine (VXA-GII.4-NS plus VXA-G1.1-NN) 1×10 to the power 11 tablets total dose is 2×10 to the power 11 IU/dose (sentinel n=10)

    Drug: Open label Bivalent GII.4/GI.1 high dose vaccine 2×10 to the power 11 IU/dose

  • Experimental
    Medium Dose Arm

    Bivalent GII.4/GI.1 vaccine Bivalent GII.4/GI.1 medium dose vaccine (VXA-GII.4-NS plus VXA-G1.1-NN) 5×10 to the power 10 tablets total dose is 1×10 to the power 11 IU/dose (N=50)

    Drug: Bivalent GII.4/GI.1 medium dose vaccine 1×10 to the power 11 IU/dose

  • Experimental
    High Dose Arm

    Bivalent GII.4/GI.1 vaccine Bivalent GII.4/GI.1 high dose vaccine (VXA-GII.4-NS plus VXA-G1.1-NN) 1×10 to the power 11 tablets total dose is 2×10 to the power 11 IU/dose (N=50)

    Drug: Bivalent GII.4/GI.1 high dose vaccine 2×10 to the power 11 IU/dose

  • Placebo comparator
    Placebo Arm

    Placebo tablets (N= 25)

    Drug: Placebo

Interventions

  • DrugOpen label Bivalent GII.4/GI.1 high dose vaccine 2×10 to the power 11 IU/dose

    The first 10 sentinel subjects will receive open label high dose of active vaccine. Bivalent GII.4/GI.1 high dose vaccine (VXA-GII.4-NS plus VXA-G1.1-NN) 1×10 to the power 11 tablets; total dose is 2×10 to the power 11 IU/dose

  • DrugBivalent GII.4/GI.1 high dose vaccine 2×10 to the power 11 IU/dose

    50 subjects will receive high dose of active vaccine. Bivalent GII.4/GI.1 high dose vaccine (VXA-GII.4-NS plus VXA-G1.1-NN) 1×10 to the power 11 tablets; total dose is 2×10 to the power 11 IU/dose

  • DrugBivalent GII.4/GI.1 medium dose vaccine 1×10 to the power 11 IU/dose

    50 subjects will receive Bivalent GII.4/GI.1 medium dose vaccine (VXA-GII.4-NS plus VXA-G1.1-NN) 5×10 to the power 10 tablets; total dose is 1×10 to the power 11 IU/dose

  • DrugPlacebo

    25 subjects will receive matching placebo

06

What researchers measure

Primary outcomes

  1. Number of Participants With Solicited Symptoms of Reactogenicity (Gastrointestinal [GI] and Systemic)

    Solicited adverse events (AEs) are predefined signs and symptoms of reactogenicity for which the participants were specifically questioned, and which were noted by the participant in their Solicited Symptom Diary for 7 days after drug administration, including: * fever (any temperature 100.4°F or higher) * headache * myalgia (muscle pain) * abdominal pain * anorexia (defined as not eating) * nausea * vomiting * diarrhoea * malaise/fatigue. The severity of each solicited symptoms of reactogenicity was graded by the participant as mild, moderate, severe or life-threatening. Participants with multiple Solicited AEs were only counted once in summarizing overall percentages of Solicited AEs, the highest severity of which was used.

    Time frame: Up to Day 8

  2. Number of Participants With Unsolicited AEs

    Treatment emergent AEs (TEAEs) are defined as AEs that occurred following the first administration of study medication. An unsolicited AE is an observed AE that did not fulfill the conditions prelisted in terms of diagnosis and/or onset window post-vaccination. The severity of each AE was graded by the participant as mild, moderate or severe/ life-threatening.

    Time frame: Up to Day 29

  3. Serum - Anti-Vaccine Protein 1 (VP1) GI.1 Immunoglobulin A (IgA) Levels by Meso Scale Discovery (MSD) Assay

    Serum levels of Anti-VP1 GI.1 IgA were evaluated using cellular and humoral immune (HI) function assays from blood and mucosal (saliva and nasal swab) samples. 95% confidence intervals were estimated by Clopper-Pearson exact method. Assay is measured in AU/mL.

    Time frame: Day 1 and Day 29

  4. Fold Rise in Serum - Anti-VP1 GI.1 IgA Levels by MSD Assay

    Serum levels of Anti-VP1 GI.1 IgA were evaluated using cellular and HI function assays from blood and mucosal (saliva and nasal swab) samples. The fold rise was calculated per participant by dividing the antibody concentration (original scale) on Day 29 with antibody concentration at baseline (Day 1). 95% confidence intervals were estimated by Clopper-Pearson exact method.

    Time frame: Day 1 and Day 29

  5. Serum - Anti-VP1 GII.4 IgGA Levels by MSD Assay

    Serum levels of Anti-VP1 GII.4 IgA were evaluated using cellular and HI function assays from blood and mucosal (saliva and nasal swab) samples. 95% confidence intervals were estimated by Clopper-Pearson exact method. Assay is measured in AU/mL.

    Time frame: Day 1 and Day 29

  6. Fold Rise in Serum - Anti-VP1 GII.4 IgA Levels by MSD Assay

    Serum levels of Anti-VP1 GII.4 IgA were evaluated using cellular and HI function assays from blood and mucosal (saliva and nasal swab) samples. The fold rise was calculated per participant by dividing the antibody concentration (original scale) on Day 29 with antibody concentration at baseline (Day 1). 95% confidence intervals were estimated by Clopper-Pearson exact method.

    Time frame: Day 1 and Day 29

  7. Serum - Anti-VP1 GI.1 Immunoglobulin G (IgG) Levels by MSD Assay

    Serum levels of Anti-VP1 GI.1 IgG were evaluated using cellular and HI function assays from blood and mucosal (saliva and nasal swab) samples. 95% confidence intervals were estimated by Clopper-Pearson exact method. Assay is measured in AU/mL.

    Time frame: Day 1 and Day 29

  8. Fold Rise in Serum - Anti-VP1 GI.1 IgG Levels by MSD Assay

    Serum levels of Anti-VP1 GI.1 IgG were evaluated using cellular and HI function assays from blood and mucosal (saliva and nasal swab) samples. The fold rise was calculated per participant by dividing the antibody concentration (original scale) on Day 29 with antibody concentration at baseline (Day 1). 95% confidence intervals were estimated by Clopper-Pearson exact method.

    Time frame: Day 1 and Day 29

  9. Serum - Anti-VP1 GII.4 IgG Levels by MSD Assay

    Serum levels of Anti-VP1 GII.4 IgG were evaluated using cellular and HI function assays from blood and mucosal (saliva and nasal swab) samples. 95% confidence intervals were estimated by Clopper-Pearson exact method. Assay is measured in AU/mL.

    Time frame: Day 1 and Day 29

  10. Fold Rise in Serum - Anti-VP1 GII.4 IgG Levels by MSD Assay

    Serum levels of Anti-VP1 GII.4 IgG were evaluated using cellular and HI function assays from blood and mucosal (saliva and nasal swab) samples. The fold rise was calculated per participant by dividing the antibody concentration (original scale) on Day 29 with antibody concentration at baseline (Day 1). 95% confidence intervals were estimated by Clopper-Pearson exact method.

    Time frame: Day 1 and Day 29

  11. Serum - Anti-VP1 GI.1 Blocking Antibodies (BT50) Titers by MSD Assay

    Serum levels of Anti-VP1 GI.1 BT50 were evaluated using cellular and HI function assays from blood and mucosal (saliva and nasal swab) samples. 95% confidence intervals were estimated by Clopper-Pearson exact method.

    Time frame: Day 1 and Day 29

  12. Fold Rise in Serum - Anti-VP1 GI.1 BT50 Titers by MSD Assay

    Serum levels of Anti-VP1 GI.1 BT50 were evaluated using cellular and HI function assays from blood and mucosal (saliva and nasal swab) samples. The fold rise was calculated per participant by dividing the antibody concentration (original scale) on Day 29 with antibody concentration at baseline (Day 1).

    Time frame: Day 1 and Day 29

  13. Serum - Anti-VP1 GII.4 BT50 Titers by MSD Assay

    Serum levels of Anti-VP1 GII.4 BT50 were evaluated using cellular and HI function assays from blood and mucosal (saliva and nasal swab) samples. 95% confidence intervals were estimated by Clopper-Pearson exact method.

    Time frame: Day 1 and Day 29

  14. Fold Rise in Serum - Anti-VP1 GII.4 BT50 Titers by MSD Assay

    Serum levels of Anti-VP1 GII.4 BT50 were evaluated using cellular and HI function assays from blood and mucosal (saliva and nasal swab) samples. The fold rise was calculated per participant by dividing the antibody concentration (original scale) on Day 29 with antibody concentration at baseline (Day 1). 95% confidence intervals were estimated by Clopper-Pearson exact method.

    Time frame: Day 1 and Day 29

07

Results

Posted Apr 15, 2025

Participant flow

A total of 135 participants were enrolled between January 2023 and October 2023 in the Unites States.

Participant flow — Overall Study
MilestoneBivalent GI.1/GII.4 Vaccine Medium DoseBivalent GI.1/GII.4 Vaccine High DoseSentinels Open Label High DosePlacebo
Started50501025
Completed50491025
Not completed0100
Withdrew: Lost to follow-up0100

Outcome measures

PrimaryNumber of Participants With Solicited Symptoms of Reactogenicity (Gastrointestinal [GI] and Systemic)

Solicited adverse events (AEs) are predefined signs and symptoms of reactogenicity for which the participants were specifically questioned, and which were noted by the participant in their Solicited Symptom Diary for 7 days after drug administration, including: * fever (any temperature 100.4°F or higher) * headache * myalgia (muscle pain) * abdominal pain * anorexia (defined as not eating) * nausea * vomiting * diarrhoea * malaise/fatigue. The severity of each solicited symptoms of reactogenicity was graded by the participant as mild, moderate, severe or life-threatening. Participants with multiple Solicited AEs were only counted once in summarizing overall percentages of Solicited AEs, the highest severity of which was used.

Time frame:
Up to Day 8
Reported as:
Count of participants · Participants
Number of Participants With Solicited Symptoms of Reactogenicity (Gastrointestinal [GI] and Systemic)
ParticipantsBivalent GI.1/GII.4 Vaccine Medium DoseBivalent GI.1/GII.4 Vaccine High DoseSentinels Open Label High DosePlacebo
Mild202029
Moderate3915
Severe0000
Life-threatening0000
PrimaryNumber of Participants With Unsolicited AEs

Treatment emergent AEs (TEAEs) are defined as AEs that occurred following the first administration of study medication. An unsolicited AE is an observed AE that did not fulfill the conditions prelisted in terms of diagnosis and/or onset window post-vaccination. The severity of each AE was graded by the participant as mild, moderate or severe/ life-threatening.

Time frame:
Up to Day 29
Reported as:
Count of participants · Participants
Number of Participants With Unsolicited AEs
ParticipantsBivalent GI.1/GII.4 Vaccine Medium DoseBivalent GI.1/GII.4 Vaccine High DoseSentinels Open Label High DosePlacebo
Mild5923
Moderate3101
Severe/ Life-threatening0001
PrimarySerum - Anti-Vaccine Protein 1 (VP1) GI.1 Immunoglobulin A (IgA) Levels by Meso Scale Discovery (MSD) Assay

Serum levels of Anti-VP1 GI.1 IgA were evaluated using cellular and humoral immune (HI) function assays from blood and mucosal (saliva and nasal swab) samples. 95% confidence intervals were estimated by Clopper-Pearson exact method. Assay is measured in AU/mL.

Time frame:
Day 1 and Day 29
Reported as:
Geometric mean · AU/mL
Serum - Anti-Vaccine Protein 1 (VP1) GI.1 Immunoglobulin A (IgA) Levels by Meso Scale Discovery (MSD) Assay
AU/mLBivalent GI.1/GII.4 Vaccine Medium DoseBivalent GI.1/GII.4 Vaccine High DoseSentinels Open Label High DosePlacebo
Day 1461471.1 (294526.0 to 723045.2)519763.7 (318805.2 to 847396.3)149810.3 (47236.2 to 475125.2)533470.9 (255503.2 to 1113846.0)
Day 291456125.4 (956707.8 to 2216247.4)1913341.7 (1257483.5 to 2911272.0)657853.4 (248820.3 to 1739291.7)545855.7 (259791.3 to 1146914.6)
PrimaryFold Rise in Serum - Anti-VP1 GI.1 IgA Levels by MSD Assay

Serum levels of Anti-VP1 GI.1 IgA were evaluated using cellular and HI function assays from blood and mucosal (saliva and nasal swab) samples. The fold rise was calculated per participant by dividing the antibody concentration (original scale) on Day 29 with antibody concentration at baseline (Day 1). 95% confidence intervals were estimated by Clopper-Pearson exact method.

Time frame:
Day 1 and Day 29
Reported as:
Geometric mean · Fold Rise
Fold Rise in Serum - Anti-VP1 GI.1 IgA Levels by MSD Assay
Fold RiseBivalent GI.1/GII.4 Vaccine Medium DoseBivalent GI.1/GII.4 Vaccine High DoseSentinels Open Label High DosePlacebo
Fold Rise in Serum - Anti-VP1 GI.1 IgA Levels by MSD Assay3.16 (2.35 to 4.24)3.68 (2.80 to 4.84)4.39 (2.22 to 8.68)1.02 (0.95 to 1.10)
Statistical analysis
  • Bivalent GI.1/GII.4 Vaccine Medium Dose vs Placebo · ANCOVA · p = <.0001Computed by using ANCOVA model with log transformed data as response variable and treatment as a fixed factor and baseline value as covariate.
  • Bivalent GI.1/GII.4 Vaccine High Dose vs Placebo · ANCOVA · p = <.0001Computed by using ANCOVA model with log transformed data as response variable and treatment as a fixed factor and baseline value as covariate.
  • Sentinels Open Label High Dose vs Placebo · ANCOVA · p = 0.0003Computed by using ANCOVA model with log transformed data as response variable and treatment as a fixed factor and baseline value as covariate.
PrimarySerum - Anti-VP1 GII.4 IgGA Levels by MSD Assay

Serum levels of Anti-VP1 GII.4 IgA were evaluated using cellular and HI function assays from blood and mucosal (saliva and nasal swab) samples. 95% confidence intervals were estimated by Clopper-Pearson exact method. Assay is measured in AU/mL.

Time frame:
Day 1 and Day 29
Reported as:
Geometric mean · AU/mL
Serum - Anti-VP1 GII.4 IgGA Levels by MSD Assay
AU/mLBivalent GI.1/GII.4 Vaccine Medium DoseBivalent GI.1/GII.4 Vaccine High DoseSentinels Open Label High DosePlacebo
Day 1161875.6 (94846.4 to 276275.2)259428.2 (161931.1 to 415627.3)210263.7 (59975.1 to 737152.9)154353.5 (67958.7 to 350580.5)
Day 29660009.0 (417023.3 to 1044574.4)1132279.0 (789453.9 to 1623977.9)1213636.4 (616105.1 to 2390685.1)185430.7 (81633.1 to 421208.4)
PrimaryFold Rise in Serum - Anti-VP1 GII.4 IgA Levels by MSD Assay

Serum levels of Anti-VP1 GII.4 IgA were evaluated using cellular and HI function assays from blood and mucosal (saliva and nasal swab) samples. The fold rise was calculated per participant by dividing the antibody concentration (original scale) on Day 29 with antibody concentration at baseline (Day 1). 95% confidence intervals were estimated by Clopper-Pearson exact method.

Time frame:
Day 1 and Day 29
Reported as:
Geometric mean · Fold Rise
Fold Rise in Serum - Anti-VP1 GII.4 IgA Levels by MSD Assay
Fold RiseBivalent GI.1/GII.4 Vaccine Medium DoseBivalent GI.1/GII.4 Vaccine High DoseSentinels Open Label High DosePlacebo
Fold Rise in Serum - Anti-VP1 GII.4 IgA Levels by MSD Assay4.07 (2.78 to 5.98)4.36 (3.25 to 5.85)5.78 (1.82 to 18.33)1.20 (0.82 to 1.75)
Statistical analysis
  • Bivalent GI.1/GII.4 Vaccine Medium Dose vs Placebo · ANCOVA · p = <.0001Computed by using ANCOVA model with log transformed data as response variable and treatment as a fixed factor and baseline value as covariate.
  • Bivalent GI.1/GII.4 Vaccine High Dose vs Placebo · ANCOVA · p = <.0001Computed by using ANCOVA model with log transformed data as response variable and treatment as a fixed factor and baseline value as covariate.
  • Sentinels Open Label High Dose vs Placebo · ANCOVA · p = <.0001Computed by using ANCOVA model with log transformed data as response variable and treatment as a fixed factor and baseline value as covariate.
PrimarySerum - Anti-VP1 GI.1 Immunoglobulin G (IgG) Levels by MSD Assay

Serum levels of Anti-VP1 GI.1 IgG were evaluated using cellular and HI function assays from blood and mucosal (saliva and nasal swab) samples. 95% confidence intervals were estimated by Clopper-Pearson exact method. Assay is measured in AU/mL.

Time frame:
Day 1 and Day 29
Reported as:
Geometric mean · AU/mL
Serum - Anti-VP1 GI.1 Immunoglobulin G (IgG) Levels by MSD Assay
AU/mLBivalent GI.1/GII.4 Vaccine Medium DoseBivalent GI.1/GII.4 Vaccine High DoseSentinels Open Label High DosePlacebo
Day 1581088.4 (375777.2 to 898574.5)413505.3 (271032.1 to 630872.5)227560.5 (77474.5 to 668397.0)585351.0 (324390.2 to 1056245.7)
Day 291612583.2 (1089047.2 to 2387797.7)1203384.0 (810726.2 to 1786216.9)670462.8 (225913.2 to 1989792.5)575375.0 (315269.9 to 1050073.1)
PrimaryFold Rise in Serum - Anti-VP1 GI.1 IgG Levels by MSD Assay

Serum levels of Anti-VP1 GI.1 IgG were evaluated using cellular and HI function assays from blood and mucosal (saliva and nasal swab) samples. The fold rise was calculated per participant by dividing the antibody concentration (original scale) on Day 29 with antibody concentration at baseline (Day 1). 95% confidence intervals were estimated by Clopper-Pearson exact method.

Time frame:
Day 1 and Day 29
Reported as:
Geometric mean · Fold Rise
Fold Rise in Serum - Anti-VP1 GI.1 IgG Levels by MSD Assay
Fold RiseBivalent GI.1/GII.4 Vaccine Medium DoseBivalent GI.1/GII.4 Vaccine High DoseSentinels Open Label High DosePlacebo
Fold Rise in Serum - Anti-VP1 GI.1 IgG Levels by MSD Assay2.78 (2.07 to 3.72)2.91 (2.29 to 3.71)2.95 (2.25 to 3.86)0.98 (0.93 to 1.04)
Statistical analysis
  • Bivalent GI.1/GII.4 Vaccine Medium Dose vs Placebo · ANCOVA · p = <.0001Computed by using ANCOVA model with log transformed data as response variable and treatment as a fixed factor and baseline value as covariate.
  • Bivalent GI.1/GII.4 Vaccine High Dose vs Placebo · ANCOVA · p = <.0001Computed by using ANCOVA model with log transformed data as response variable and treatment as a fixed factor and baseline value as covariate.
  • Sentinels Open Label High Dose vs Placebo · ANCOVA · p = 0.0017Computed by using ANCOVA model with log transformed data as response variable and treatment as a fixed factor and baseline value as covariate.
PrimarySerum - Anti-VP1 GII.4 IgG Levels by MSD Assay

Serum levels of Anti-VP1 GII.4 IgG were evaluated using cellular and HI function assays from blood and mucosal (saliva and nasal swab) samples. 95% confidence intervals were estimated by Clopper-Pearson exact method. Assay is measured in AU/mL.

Time frame:
Day 1 and Day 29
Reported as:
Geometric mean · AU/mL
Serum - Anti-VP1 GII.4 IgG Levels by MSD Assay
AU/mLBivalent GI.1/GII.4 Vaccine Medium DoseBivalent GI.1/GII.4 Vaccine High DoseSentinels Open Label High DosePlacebo
Day 1271643.8 (187461.8 to 393628.7)242957.4 (166040.8 to 355504.8)213650.0 (90624.7 to 503685.4)252459.1 (145831.9 to 437048.4)
Day 29800970.2 (583219.1 to 1100021.2)837784.5 (594378.9 to 1180867.6)841249.4 (402948.8 to 1756303.8)247733.5 (142572.8 to 430459.9)
PrimaryFold Rise in Serum - Anti-VP1 GII.4 IgG Levels by MSD Assay

Serum levels of Anti-VP1 GII.4 IgG were evaluated using cellular and HI function assays from blood and mucosal (saliva and nasal swab) samples. The fold rise was calculated per participant by dividing the antibody concentration (original scale) on Day 29 with antibody concentration at baseline (Day 1). 95% confidence intervals were estimated by Clopper-Pearson exact method.

Time frame:
Day 1 and Day 29
Reported as:
Geometric mean · Fold Rise
Fold Rise in Serum - Anti-VP1 GII.4 IgG Levels by MSD Assay
Fold RiseBivalent GI.1/GII.4 Vaccine Medium DoseBivalent GI.1/GII.4 Vaccine High DoseSentinels Open Label High DosePlacebo
Fold Rise in Serum - Anti-VP1 GII.4 IgG Levels by MSD Assay2.95 (2.15 to 4.04)3.45 (2.70 to 4.40)3.94 (2.01 to 7.70)0.98 (0.89 to 1.09)
Statistical analysis
  • Bivalent GI.1/GII.4 Vaccine Medium Dose vs Placebo · ANCOVA · p = <.0001Computed by using ANCOVA model with log transformed data as response variable and treatment as a fixed factor and baseline value as covariate.
  • Bivalent GI.1/GII.4 Vaccine High Dose vs Placebo · ANCOVA · p = <.0001Computed by using ANCOVA model with log transformed data as response variable and treatment as a fixed factor and baseline value as covariate.
  • Sentinels Open Label High Dose vs Placebo · ANCOVA · p = <.0001Computed by using ANCOVA model with log transformed data as response variable and treatment as a fixed factor and baseline value as covariate.
PrimarySerum - Anti-VP1 GI.1 Blocking Antibodies (BT50) Titers by MSD Assay

Serum levels of Anti-VP1 GI.1 BT50 were evaluated using cellular and HI function assays from blood and mucosal (saliva and nasal swab) samples. 95% confidence intervals were estimated by Clopper-Pearson exact method.

Time frame:
Day 1 and Day 29
Reported as:
Geometric mean · Titer
Serum - Anti-VP1 GI.1 Blocking Antibodies (BT50) Titers by MSD Assay
TiterBivalent GI.1/GII.4 Vaccine Medium DoseBivalent GI.1/GII.4 Vaccine High DoseSentinels Open Label High DosePlacebo
Day 141.9 (29.5 to 59.6)41.3 (28.0 to 60.9)20.3 (10.5 to 39.4)40.6 (21.7 to 76.0)
Day 2971.2 (49.6 to 102.3)75.4 (50.5 to 112.5)33.0 (13.3 to 82.1)42.3 (23.5 to 76.4)
PrimaryFold Rise in Serum - Anti-VP1 GI.1 BT50 Titers by MSD Assay

Serum levels of Anti-VP1 GI.1 BT50 were evaluated using cellular and HI function assays from blood and mucosal (saliva and nasal swab) samples. The fold rise was calculated per participant by dividing the antibody concentration (original scale) on Day 29 with antibody concentration at baseline (Day 1).

Time frame:
Day 1 and Day 29
Reported as:
Geometric mean · Fold Rise
Fold Rise in Serum - Anti-VP1 GI.1 BT50 Titers by MSD Assay
Fold RiseBivalent GI.1/GII.4 Vaccine Medium DoseBivalent GI.1/GII.4 Vaccine High DoseSentinels Open Label High DosePlacebo
Fold Rise in Serum - Anti-VP1 GI.1 BT50 Titers by MSD Assay1.71 (1.29 to 2.27)1.82 (1.50 to 2.22)1.62 (1.01 to 2.60)1.04 (0.89 to 1.23)
Statistical analysis
  • Bivalent GI.1/GII.4 Vaccine Medium Dose vs Placebo · ANCOVA · p = 0.0059Computed by using ANCOVA model with log transformed data as response variable and treatment as a fixed factor and baseline value as covariate.
  • Bivalent GI.1/GII.4 Vaccine High Dose vs Placebo · ANCOVA · p = 0.0020Computed by using ANCOVA model with log transformed data as response variable and treatment as a fixed factor and baseline value as covariate.
  • Sentinels Open Label High Dose vs Placebo · ANCOVA · p = 0.1899Computed by using ANCOVA model with log transformed data as response variable and treatment as a fixed factor and baseline value as covariate.
PrimarySerum - Anti-VP1 GII.4 BT50 Titers by MSD Assay

Serum levels of Anti-VP1 GII.4 BT50 were evaluated using cellular and HI function assays from blood and mucosal (saliva and nasal swab) samples. 95% confidence intervals were estimated by Clopper-Pearson exact method.

Time frame:
Day 1 and Day 29
Reported as:
Geometric mean · Titer
Serum - Anti-VP1 GII.4 BT50 Titers by MSD Assay
TiterBivalent GI.1/GII.4 Vaccine Medium DoseBivalent GI.1/GII.4 Vaccine High DoseSentinels Open Label High DosePlacebo
Day 142.0 (29.4 to 60.0)51.8 (36.6 to 73.4)48.3 (23.4 to 99.7)38.4 (23.4 to 63.2)
Day 29108.7 (80.3 to 147.0)138.5 (100.9 to 190.0)123.1 (64.1 to 236.5)40.6 (25.1 to 65.6)
PrimaryFold Rise in Serum - Anti-VP1 GII.4 BT50 Titers by MSD Assay

Serum levels of Anti-VP1 GII.4 BT50 were evaluated using cellular and HI function assays from blood and mucosal (saliva and nasal swab) samples. The fold rise was calculated per participant by dividing the antibody concentration (original scale) on Day 29 with antibody concentration at baseline (Day 1). 95% confidence intervals were estimated by Clopper-Pearson exact method.

Time frame:
Day 1 and Day 29
Reported as:
Geometric mean · Fold Rise
Fold Rise in Serum - Anti-VP1 GII.4 BT50 Titers by MSD Assay
Fold RiseBivalent GI.1/GII.4 Vaccine Medium DoseBivalent GI.1/GII.4 Vaccine High DoseSentinels Open Label High DosePlacebo
Fold Rise in Serum - Anti-VP1 GII.4 BT50 Titers by MSD Assay2.58 (1.96 to 3.40)2.67 (1.95 to 3.65)2.55 (1.33 to 4.89)1.06 (0.92 to 1.22)
Statistical analysis
  • Bivalent GI.1/GII.4 Vaccine Medium Dose vs Placebo · ANCOVA · p = <.0001Computed by using ANCOVA model with log transformed data as response variable and treatment as a fixed factor and baseline value as covariate.
  • Bivalent GI.1/GII.4 Vaccine High Dose vs Placebo · ANCOVA · p = <.0001Computed by using ANCOVA model with log transformed data as response variable and treatment as a fixed factor and baseline value as covariate.
  • Sentinels Open Label High Dose vs Placebo · ANCOVA · p = 0.0020Computed by using ANCOVA model with log transformed data as response variable and treatment as a fixed factor and baseline value as covariate.

Adverse events

Collected over For TEAEs: Up to Day 29 For SAEs and all-cause mortality: Up to Day 180. Non-serious events are listed at a 0% frequency threshold.

Adverse event summary by group
GroupDeathsSeriousOther
Bivalent GI.1/GII.4 Vaccine Medium Dose0/50 (0%)0/50 (0%)8/50 (16%)
Bivalent GI.1/GII.4 Vaccine High Dose0/50 (0%)0/50 (0%)10/50 (20%)
Sentinels Open Label High Dose0/10 (0%)0/10 (0%)2/10 (20%)
Placebo0/25 (0%)0/25 (0%)5/25 (20%)
Most frequent other events
Showing 10 of 26
Most frequent other events
EventBivalent GI.1/GII.4 Vaccine Medium DoseBivalent GI.1/GII.4 Vaccine High DoseSentinels Open Label High DosePlacebo
COVID-19Infections and infestations0/500/501/100/25
Urinary tract infectionInfections and infestations0/500/501/100/25
MyalgiaMusculoskeletal and connective tissue disorders0/500/501/100/25
GastroenteritisInfections and infestations0/500/500/101/25
HeadacheNervous system disorders2/501/500/101/25
Back painMusculoskeletal and connective tissue disorders0/500/500/101/25
Pain in extremityMusculoskeletal and connective tissue disorders0/500/500/101/25
FlatulenceGastrointestinal disorders0/502/500/100/25
FatigueGeneral disorders0/500/500/101/25
Tooth fractureInjury, poisoning and procedural complications0/500/500/101/25

Baseline characteristics

Safety Analysis Set (SAF): All randomized participants who received at least 1 dose of the study drug. Participants were analyzed according to the treatment (vaccine) they actually received.

Age, Categorical
Age, Categorical(Participants)Bivalent GI.1/GII.4 Vaccine Medium DoseBivalent GI.1/GII.4 Vaccine High DoseSentinels Open Label High DosePlaceboTotal
<=18 years00000
Between 18 and 65 years44471025126
>=65 years63009
Sex: Female, Male
Sex: Female, Male(Participants)Bivalent GI.1/GII.4 Vaccine Medium DoseBivalent GI.1/GII.4 Vaccine High DoseSentinels Open Label High DosePlaceboTotal
Female242051160
Male263051475
Ethnicity (NIH/OMB)
Ethnicity (NIH/OMB)(Participants)Bivalent GI.1/GII.4 Vaccine Medium DoseBivalent GI.1/GII.4 Vaccine High DoseSentinels Open Label High DosePlaceboTotal
Hispanic or Latino812415
Not Hispanic or Latino4248821119
Unknown or Not Reported01001
Race (NIH/OMB)
Race (NIH/OMB)(Participants)Bivalent GI.1/GII.4 Vaccine Medium DoseBivalent GI.1/GII.4 Vaccine High DoseSentinels Open Label High DosePlaceboTotal
American Indian or Alaska Native00101
Asian631414
Native Hawaiian or Other Pacific Islander00011
Black or African American10111325
White323471790
More than one race22004
Unknown or Not Reported00000
08

Study locations

3 sites
  • Ark Clinical Research
    Long Beach, California 90806, United States
  • Johnson County Clin-Trials
    Lenexa, Kansas 66219, United States
  • Nucleus Network Pty Ltd
    Saint Paul, Minnesota 55114, United States
09

References and documents

Study documents

  • Protocol and statistical analysis plan · Feb 22, 2023

Documents are hosted by the registry — open the source record to download them.

Individual participant data

Plan to share: No

10

Updates

Tracking since Sep 25, 2026
No changes since tracking began. The registry record was last updated on Apr 15, 2025, before this site started recording changes on Sep 25, 2026. Its history is on ClinicalTrials.gov ↗
11

Registry details

Key details

Study ID
NCT05626803
Lead sponsor
Vaxart
Responsible party
Sponsor
First posted
Nov 25, 2022
Start date
Jan 26, 2023
Primary completion
Oct 16, 2023
Completion
Oct 16, 2023
Results posted
Apr 15, 2025
Last update
Apr 15, 2025

Study contacts

James Cummings, MD
study director · Vaxart, Inc.

Oversight

Data monitoring committee
No
FDA-regulated drug
Yes
FDA-regulated device
No
View the source record on ClinicalTrials.gov ↗

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