H1N1v Virus Challenge Study in Healthy Subjects

A Controlled Human Infection Study of Influenza A/Bethesda/MM2/H1N1 Virus (A/California/04/2009/H1N1-like) in Healthy Subjects to Assess the Effect of Pre-Existing Immunity on Symptomatic Influenza Virus Infection

Status

Completed

Phases

Phase 1

Study type

Interventional

Source

ClinicalTrials.gov

Registry ID

NCT04044352

Enrollment

Registered

2019-08-05

Start date

2019-10-22

Completion date

2020-03-02

Last updated

2021-04-28

For informational purposes only — not medical advice. Sourced from public registries and may not reflect the latest updates. Terms

Conditions

Influenza

Keywords

A/Bethesda/MM2/H1N1 Virus, Challenge, Dose Escalation, Healthy Subjects, Influenza, Live virus

Brief summary

Detailed description

This is a study of a reverse-engineered, Good Manufacturing Practice (GMP) grade, antiviral-sensitive, influenza A/Bethesda/MM2/H1N1 virus (A/California/04/2009/H1N1-like) infection to assess the effect of pre-existing immunity on clinical and immunological responses. Up to 80 healthy adult subjects will undergo intranasal inoculation with A/Bethesda/MM2/H1N1 virus, and their clinical manifestations, viral shedding and immunological responses will be characterized. This proposed study will establish a H1N1 influenza virus controlled human infection (CHI) model at the National Institute of Allergy and Infectious Diseases (NIAID) Division of Microbiology and Infectious Diseases (DMID)-sponsored Vaccine and Treatment Evaluation Units (VTEU) clinical study sites. The model has been developed and used by NIAID Division of Intramural Research. The proposed study will expand US research capacity to perform influenza CHI studies to advance the understanding of influenza pathogenesis and novel vaccine research and development. The Primary Objective for this study is to evaluate the association of symptomatic Reverse Transcription-Polymerase Chain Reaction (RT-PCR)-positive influenza virus infection post-challenge and pre-existing Hemagglutinin Inhibition Test (HAI) antibody titers. The Secondary Objectives for this study are: 1) To describe viral recovery by quantitative RT-PCR from study subjects at baseline and post-challenge; 2) To describe serum HAI and MN antibody responses post-challenge in healthy subjects by infection status; 3) To evaluate the association of asymptomatic RT-PCR-positive influenza virus infection (viral shedding) post-challenge and pre-existing HAI antibody titers; 4) To evaluate the association of symptomatic RT-PCR-negative status post-challenge and pre-existing HAI antibody titers; 5) To determine the frequency of serious adverse events (SAE) post-challenge.

Interventions

BIOLOGICALInfluenza A/Bethesda/MM2/H1N1 Challenge

Reverse-genetics derived live A/California/04/2009/H1N1-like influenza virus passaged six times in Vero cells.

Study design

Allocation

Intervention model

SINGLE_GROUP

Primary purpose

BASIC_SCIENCE

Masking

NONE

Eligibility

Sex/Gender

ALL

Age

18 Years to 49 Years

Healthy volunteers

Yes

Inclusion criteria

1. Provide written informed consent prior to initiation of any study procedure. 2. Are able to understand and comply with planned study procedures and be available for all study visits. 3. Agree to remain an inpatient for at least seven days after challenge, and until they have no virus shedding,\* determined by qualitative RT-PCR for a minimum of two consecutive days post-challenge. * For a minimum of seven days post-challenge (Study Day 8). 4. Healthy\* males and non-pregnant, non-breastfeeding females\*\*, aged \>/= 18 and \</=49 years of age, inclusive, at enrollment. \*Good health is defined in inclusion criteria 10. * Females subjects of childbearing potential must agree to have a serum pregnancy test at screening, a urine pregnancy test before Chest X-Ray (CXR) performed (if more than 7 days have passed between CXR and serum pregnancy test), and a urine pregnancy test upon admission to the inpatient unit prior to CHI, and results must be negative. 5. Women of childbearing potential\* must agree to use or have practiced true abstinence\*\* or use at least 1 acceptable primary form of contraception\*\*\*,\*\*\*\*. These criteria are applicable to females in a heterosexual relationship and child-bearing potential (i.e., the criteria do not apply to subjects in a same sex relationship). \*Not of child bearing potential - post-menopausal females (defined as having a history of amenorrhea for at least one year) or a documented status as being surgically sterile (hysterectomy, bilateral oophorectomy, tubal ligation/salpingectomy, or Essure(R) placement with history of documented radiological confirmation test at least 90 days after the procedure). \*\*True abstinence is 100% of time no sexual intercourse (male's penis enters the female's vagina). (Periodic abstinence \[e.g. calendar, ovulation, symptothermal, post-ovulation methods\] and withdrawal are not acceptable methods of contraception). \*\*\*Acceptable forms of primary contraception include monogamous relationship with a vasectomized partner who has been vasectomized for180 days or more prior to the subject receiving the influenza challenge virus, intrauterine devices, birth control pills, and injectable/implantable/insertable hormonal birth control products. \*\*\*\*Must use at least one acceptable primary form of contraception for at least 30 days prior to admission and at least one acceptable primary form of contraception during the remainder of the study. 6. Non-habitual smoker\* of tobacco, e-cigarettes or marijuana. \*Non-habitual smokers are those who smoke no more than four cigarettes, other tobacco products, e-cigarettes or marijuana in a week for more than three months and agree not to smoke cigarettes, other tobacco products, e-cigarettes and/or marijuana products during participation in the study. 7. No self-reported or known history of alcoholism or drug use within the last 30 days and agrees to abstain from alcohol and drugs\* for at least one week before admission and throughout the inpatient period. \*Including forms of marijuana not included in criterion 6. 8. Negative drug urine toxicology result on screening (i.e., amphetamines, cocaine, and opiates) and on admission to the challenge unit (i.e., amphetamines, cocaine, opiates, and cannabinoids). 9. Agree not to use the listed\* prescription or over-the-counter medications within 7 days prior to inpatient stay and through inpatient stay, unless approved by the investigator. \*Oseltamivir, zanamivir, peramivir, baloxavir marboxil, amantadine (generic) and rimantadine (Flumadine and generic), aspirin, intranasal steroids, decongestants, antihistamines, and other non-steroidal anti-inflammatory drugs (NSAIDs). 10. In good health\* and not have clinically significant medical, psychiatric, chronic or intermittent health conditions including those listed in the Subject

Exclusion criteria

. \*Good health, as determined by medical history, medication use and physical examination to evaluate ongoing chronic medical or psychiatric diagnoses or conditions, defined as those that have been present for at least 90 days, which would not affect the assessment of the safety of subjects or the immunogenicity of challenge. These medical diagnoses or conditions should be stable for the last 90 days (no hospitalizations, emergency room (ER) or urgent care for condition (excluding musculoskeletal conditions) and not listed in the Subject

Design outcomes

Primary

Measure	Time frame	Description
Percentage of Healthy Participants Reporting Mild-to-Moderate Influenza Disease (MMID) by Baseline A/Bethesda/MM2/H1N1 Hemagglutination Inhibition (HAI) Antibody Seroprotection Status (Titer >/= 1:40 vs. Titer < 1:40)	Day 2 through Day 8	Blood samples were collected pre-challenge (Day -2) for the HAI assay conducted with the A/Bethesda/MM2/H1N1 virus as the antigen. The geometric mean of each sample's replicate results was calculated from available results, then grouped by seroprotection status (titer results \>= 1:40 vs \< 1:40). MMID is a composite endpoint determined by the presence of viral shedding (detected by any approved positive RT-PCR test from a NP swab), accompanied by at least one the following symptoms occurring any time from Day 2 through Day 8; body aches or pain, chest tightness, chills, conjunctivitis, nasal congestion, sinus congestion, coryza, decreased appetite, diarrhea, dry cough, dyspnea, fatigue, fever, headache, lymphopenia, nausea, a 3% or more decrease in oxygen saturation from baseline, productive cough, rhinorrhea, sore throat, and sweats. The percentage of participants that developed MMID was calculated within each pre-challenge seroprotection status group.
Association Between Clinical or Laboratory Manifestation of MMID and A/Bethesda/MM2/H1N1 HAI Antibodies in Serum at Baseline	Day 2 to Day 8	Blood samples were collected pre-challenge (Day -2) for the HAI assay conducted with the A/Bethesda/MM2/H1N1 virus as the antigen. The geometric mean of each sample's replicate results was calculated from available results. MMID is a composite endpoint determined by the presence of viral shedding (detected by any approved positive RT-PCR test from a NP swab), accompanied by at least one the following symptoms occurring any time from Day 2 through Day 8; body aches or pain, chest tightness, chills, conjunctivitis, nasal congestion, sinus congestion, coryza, decreased appetite, diarrhea, dry cough, dyspnea, fatigue, fever, headache, lymphopenia, nausea, a 3% or more decrease in oxygen saturation from baseline, productive cough, rhinorrhea, sore throat, and sweats. The relationship between the level of pre-challenge HAI titer and the likelihood of developing MMID during the study challenge period (Day 2 to Day 8) was assessed via logistic regression.

Secondary

Measure	Time frame	Description
GMT of HAI Antibody in Serum at Day 8 by Infection Status	Day 8	Blood samples were collected pre-challenge (Day -2) and post-challenge on Days 8, 29 and 61 for the HAI assay conducted with the A/Bethesda/MM2/H1N1 virus as the antigen. The geometric mean of each sample's replicate results was calculated from available results. The geometric mean across samples was calculated within each study day and by infection status as observed over the study challenge period (Day 2 to Day 8); RT-PCR Negative (never positive), RT-PCR Positive Asymptomatic (participants with at least one positive PCR result but no symptoms reported), at least once RT-PCR Positive Symptomatic (or MMID).
GMT of HAI Antibody in Serum at Day 61 by Infection Status	Day 61	Blood samples were collected pre-challenge (Day -2) and post-challenge on Days 8, 29 and 61 for the HAI assay conducted with the A/Bethesda/MM2/H1N1 virus as the antigen. The geometric mean of each sample's replicate results was calculated from available results. The geometric mean across samples was calculated within each study day and by infection status as observed over the study challenge period (Day 2 to Day 8); RT-PCR Negative (never positive), RT-PCR Positive Asymptomatic (participants with at least one positive PCR result but no symptoms reported), at least once RT-PCR Positive Symptomatic (or MMID).
Percentage of Healthy Participants Achieving HAI Seroconversion From Baseline in Serum at Day 8 by Infection Status	Day 8	Blood samples were collected pre-challenge (Day -2) and post-challenge on Days 8, 29 and 61 for the HAI assay conducted with the A/Bethesda/MM2/H1N1 virus as the antigen. Seroconversion was defined as a pre-challenge titer 1:10 or greater and a minimum 4-fold rise in post-challenge antibody titer. The percentage of participants achieving seroconversion was calculated within each post-challenge study day and by infection status as observed over the study challenge period (Day 2 to Day 8); RT-PCR Negative (never positive), RT-PCR Positive Asymptomatic (participants with at least one positive PCR result but no symptoms reported), at least once RT-PCR Positive Symptomatic (or MMID).
Percentage of Healthy Participants Achieving HAI Seroconversion in Serum From Baseline at Day 29 by Infection Status	Day 29	Blood samples were collected pre-challenge (Day -2) and post-challenge on Days 8, 29 and 61 for the HAI assay conducted with the A/Bethesda/MM2/H1N1 virus as the antigen. Seroconversion was defined as a pre-challenge titer 1:10 or greater and a minimum 4-fold rise in post-challenge antibody titer. The percentage of participants achieving seroconversion was calculated within each post-challenge study day and by infection status as observed over the study challenge period (Day 2 to Day 8); RT-PCR Negative (never positive), RT-PCR Positive Asymptomatic (participants with at least one positive PCR result but no symptoms reported), at least once RT-PCR Positive Symptomatic (or MMID).
Percentage of Healthy Participants Achieving HAI Seroconversion in Serum From Baseline at Day 61 by Infection Status	Day 61	Blood samples were collected pre-challenge (Day -2) and post-challenge on Days 8, 29 and 61 for the HAI assay conducted with the A/Bethesda/MM2/H1N1 virus as the antigen. Seroconversion was defined as a pre-challenge titer 1:10 or greater and a minimum 4-fold rise in post-challenge antibody titer. The percentage of participants achieving seroconversion was calculated within each post-challenge study day and by infection status as observed over the study challenge period (Day 2 to Day 8); RT-PCR Negative (never positive), RT-PCR Positive Asymptomatic (participants with at least one positive PCR result but no symptoms reported), at least once RT-PCR Positive Symptomatic (or MMID).
GMT of Microneutralization (MN) Antibody in Serum at Baseline by Infection Status	Day -2	Blood samples were collected pre-challenge (Day -2) and post-challenge on Days 8, 29 and 61 for the MN assay conducted with the A/Bethesda/MM2/H1N1 virus as the antigen. The geometric mean of each sample's replicate results was calculated from available results. The geometric mean across samples was calculated within each study day and by infection status as observed over the study challenge period (Day 2 to Day 8); RT-PCR Negative (never positive), RT-PCR Positive Asymptomatic (participants with at least one positive PCR result but no symptoms reported), at least once RT-PCR Positive Symptomatic (or MMID).
GMT of MN Antibody in Serum at Day 8 by Infection Status	Day 8	Blood samples were collected pre-challenge (Day -2) and post-challenge on Days 8, 29 and 61 for the MN assay conducted with the A/Bethesda/MM2/H1N1 virus as the antigen. The geometric mean of each sample's replicate results was calculated from available results. The geometric mean across samples was calculated within each study day and by infection status as observed over the study challenge period (Day 2 to Day 8); RT-PCR Negative (never positive), RT-PCR Positive Asymptomatic (participants with at least one positive PCR result but no symptoms reported), at least once RT-PCR Positive Symptomatic (or MMID).
GMT of MN Antibody in Serum at Day 29 by Infection Status	Day 29	Blood samples were collected pre-challenge (Day -2) and post-challenge on Days 8, 29 and 61 for the MN assay conducted with the A/Bethesda/MM2/H1N1 virus as the antigen. The geometric mean of each sample's replicate results was calculated from available results. The geometric mean across samples was calculated within each study day and by infection status as observed over the study challenge period (Day 2 to Day 8); RT-PCR Negative (never positive), RT-PCR Positive Asymptomatic (participants with at least one positive PCR result but no symptoms reported), at least once RT-PCR Positive Symptomatic (or MMID).
GMT of MN Antibody in Serum at Day 61 by Infection Status	Day 61	Blood samples were collected pre-challenge (Day -2) and post-challenge on Days 8, 29 and 61 for the MN assay conducted with the A/Bethesda/MM2/H1N1 virus as the antigen. The geometric mean of each sample's replicate results was calculated from available results. The geometric mean across samples was calculated within each study day and by infection status as observed over the study challenge period (Day 2 to Day 8); RT-PCR Negative (never positive), RT-PCR Positive Asymptomatic (participants with at least one positive PCR result but no symptoms reported), at least once RT-PCR Positive Symptomatic (or MMID).
Percentage of Healthy Participants Achieving MN Seroconversion From Baseline in Serum at Day 8 by Infection Status	Day 8	Blood samples were collected pre-challenge (Day -2) and post-challenge on Days 8, 29 and 61 for the MN assay conducted with the A/Bethesda/MM2/H1N1 virus as the antigen. Seroconversion was defined as a pre-challenge titer 1:10 or greater and a minimum 4-fold rise in post-challenge antibody titer. The percentage of participants achieving seroconversion was calculated within each post-challenge study day and by infection status as observed over the study challenge period (Day 2 to Day 8); RT-PCR Negative (never positive), RT-PCR Positive Asymptomatic (participants with at least one positive PCR result but no symptoms reported), at least once RT-PCR Positive Symptomatic (or MMID).
Percentage of Healthy Participants Achieving MN Seroconversion From Baseline in Serum at Day 29 by Infection Status	Day 29	Blood samples were collected pre-challenge (Day -2) and post-challenge on Days 8, 29 and 61 for the MN assay conducted with the A/Bethesda/MM2/H1N1 virus as the antigen. Seroconversion was defined as a pre-challenge titer 1:10 or greater and a minimum 4-fold rise in post-challenge antibody titer. The percentage of participants achieving seroconversion was calculated within each post-challenge study day and by infection status as observed over the study challenge period (Day 2 to Day 8); RT-PCR Negative (never positive), RT-PCR Positive Asymptomatic (participants with at least one positive PCR result but no symptoms reported), at least once RT-PCR Positive Symptomatic (or MMID).
Percentage of Healthy Participants Achieving MN Seroconversion From Baseline in Serum at Day 61 by Infection Status	Day 61	Blood samples were collected pre-challenge (Day -2) and post-challenge on Days 8, 29 and 61 for the MN assay conducted with the A/Bethesda/MM2/H1N1 virus as the antigen. Seroconversion was defined as a pre-challenge titer 1:10 or greater and a minimum 4-fold rise in post-challenge antibody titer. The percentage of participants achieving seroconversion was calculated within each post-challenge study day and by infection status as observed over the study challenge period (Day 2 to Day 8); RT-PCR Negative (never positive), RT-PCR Positive Asymptomatic (participants with at least one positive PCR result but no symptoms reported), at least once RT-PCR Positive Symptomatic (or MMID).
Duration of Viral Shedding in Nasopharyngeal (NP) Swab by Baseline HAI Seroprotection Status	Day 2 through Day 15	Blood samples were collected pre-challenge (Day -2) for the HAI assay conducted with the A/Bethesda/MM2/H1N1 virus as the antigen. The geometric mean of each sample's replicate results was calculated from available results, then grouped by seroprotection status (titer results \>= 1:40 vs \< 1:40). Duration of viral shedding (detected by any approved positive RT-PCR test from NP swab) was calculated from the day of the initial positive PCR result to the day of the last positive PCR result prior to discharge from the challenge unit facility, regardless of intermittent negative PCR results. The mean duration of viral shedding was calculated among participants with detected virus within each pre-challenge HAI seroprotection status group.
Duration of Viral Shedding in NP Swab by Baseline MN Seroprotection Status	Day 2 to Day 15	Blood samples were collected pre-challenge (Day -2) for the MN assay conducted with the A/Bethesda/MM2/H1N1 virus as the antigen. The geometric mean of each sample's replicate results was calculated from available results, then grouped by seroprotection status (titer results \>= 1:40 vs \< 1:40). Duration of viral shedding (detected by any approved positive RT-PCR test from NP swab) was calculated from the day of the initial positive PCR result to the day of the last positive PCR result prior to discharge from the challenge unit facility, regardless of intermittent negative PCR results. The mean duration of viral shedding was calculated among participants with detected virus within each pre-challenge MN seroprotection status group.
Number of Participants With Viral Shedding in NP Swab at Day 2 by Baseline HAI Seroprotection Status	Day 2	Blood samples were collected pre-challenge (Day -2) for the HAI assay conducted with the A/Bethesda/MM2/H1N1 virus as the antigen. The geometric mean of each sample's replicate results was calculated for available results, then grouped by seroprotection status (titer results \>= 1:40 vs \< 1:40). The number of participants with viral shedding (detected by any approved positive RT-PCR test from a NP swab) was calculated for each study day post-challenge (Day 2 to Day 8) and at any time during the entire challenge period within each pre-challenge seroprotection status group.
Number of Participants With Viral Shedding in NP Swab at Day 3 by Baseline HAI Seroprotection Status	Day 3	Blood samples were collected pre-challenge (Day -2) for the HAI assay conducted with the A/Bethesda/MM2/H1N1 virus as the antigen. The geometric mean of each sample's replicate results was calculated for available results, then grouped by seroprotection status (titer results \>= 1:40 vs \< 1:40). The number of participants with viral shedding (detected by any approved positive RT-PCR test from a NP swab) was calculated for each study day post-challenge (Day 2 to Day 8) and at any time during the entire challenge period within each pre-challenge seroprotection status group.
Number of Participants With Viral Shedding in NP Swab at Day 4 by Baseline HAI Seroprotection Status	Day 4	Blood samples were collected pre-challenge (Day -2) for the HAI assay conducted with the A/Bethesda/MM2/H1N1 virus as the antigen. The geometric mean of each sample's replicate results was calculated for available results, then grouped by seroprotection status (titer results \>= 1:40 vs \< 1:40). The number of participants with viral shedding (detected by any approved positive RT-PCR test from a NP swab) was calculated for each study day post-challenge (Day 2 to Day 8) and at any time during the entire challenge period within each pre-challenge seroprotection status group.
Number of Participants With Viral Shedding in NP Swab at Day 5 by Baseline HAI Seroprotection Status	Day 5	Blood samples were collected pre-challenge (Day -2) for the HAI assay conducted with the A/Bethesda/MM2/H1N1 virus as the antigen. The geometric mean of each sample's replicate results was calculated for available results, then grouped by seroprotection status (titer results \>= 1:40 vs \< 1:40). The number of participants with viral shedding (detected by any approved positive RT-PCR test from a NP swab) was calculated for each study day post-challenge (Day 2 to Day 8) and at any time during the entire challenge period within each pre-challenge seroprotection status group.
Number of Participants With Viral Shedding in NP Swab at Day 6 by Baseline HAI Seroprotection Status	Day 6	Blood samples were collected pre-challenge (Day -2) for the HAI assay conducted with the A/Bethesda/MM2/H1N1 virus as the antigen. The geometric mean of each sample's replicate results was calculated for available results, then grouped by seroprotection status (titer results \>= 1:40 vs \< 1:40). The number of participants with viral shedding (detected by any approved positive RT-PCR test from a NP swab) was calculated for each study day post-challenge (Day 2 to Day 8) and at any time during the entire challenge period within each pre-challenge seroprotection status group.
Number of Participants With Viral Shedding in NP Swab at Day 7 by Baseline HAI Seroprotection Status	Day 7	Blood samples were collected pre-challenge (Day -2) for the HAI assay conducted with the A/Bethesda/MM2/H1N1 virus as the antigen. The geometric mean of each sample's replicate results was calculated for available results, then grouped by seroprotection status (titer results \>= 1:40 vs \< 1:40). The number of participants with viral shedding (detected by any approved positive RT-PCR test from a NP swab) was calculated for each study day post-challenge (Day 2 to Day 8) and at any time during the entire challenge period within each pre-challenge seroprotection status group.
Number of Participants With Viral Shedding in NP Swab at Day 8 by Baseline HAI Seroprotection Status	Day 8	Blood samples were collected pre-challenge (Day -2) for the HAI assay conducted with the A/Bethesda/MM2/H1N1 virus as the antigen. The geometric mean of each sample's replicate results was calculated for available results, then grouped by seroprotection status (titer results \>= 1:40 vs \< 1:40). The number of participants with viral shedding (detected by any approved positive RT-PCR test from a NP swab) was calculated for each study day post-challenge (Day 2 to Day 8) and at any time during the entire challenge period within each pre-challenge seroprotection status group.
Number of Participants With Viral Shedding in NP Swab Anytime Post-challenge by Baseline HAI Seroprotection Status	Day 2 to Day 8	Blood samples were collected pre-challenge (Day -2) for the HAI assay conducted with the A/Bethesda/MM2/H1N1 virus as the antigen. The geometric mean of each sample's replicate results was calculated for available results, then grouped by seroprotection status (titer results \>= 1:40 vs \< 1:40). The number of participants with viral shedding (detected by any approved positive RT-PCR test from a NP swab) was calculated for each study day post-challenge (Day 2 to Day 8) and at any time during the entire challenge period within each pre-challenge seroprotection status group.
Number of Participants With Viral Shedding in NP Swab at Day 2 by Baseline MN Seroprotection Status	Day 2	Blood samples were collected pre-challenge (Day -2) for the MN assay conducted with the A/Bethesda/MM2/H1N1 virus as the antigen. The geometric mean of each sample's replicate results was calculated for available results, then grouped by seroprotection status (titer results \>= 1:40 vs \< 1:40). The number of participants with viral shedding (detected by any approved positive RT-PCR test from a NP swab) was calculated for each study day post-challenge (Day 2 to Day 8) and at any time during the entire challenge period within each pre-challenge seroprotection status group.
Number of Participants With Viral Shedding in NP Swab at Day 3 by Baseline MN Seroprotection Status	Day 3	Blood samples were collected pre-challenge (Day -2) for the MN assay conducted with the A/Bethesda/MM2/H1N1 virus as the antigen. The geometric mean of each sample's replicate results was calculated for available results, then grouped by seroprotection status (titer results \>= 1:40 vs \< 1:40). The number of participants with viral shedding (detected by any approved positive RT-PCR test from a NP swab) was calculated for each study day post-challenge (Day 2 to Day 8) and at any time during the entire challenge period within each pre-challenge seroprotection status group.
Number of Participants With Viral Shedding in NP Swab at Day 4 by Baseline MN Seroprotection Status	Day 4	Blood samples were collected pre-challenge (Day -2) for the MN assay conducted with the A/Bethesda/MM2/H1N1 virus as the antigen. The geometric mean of each sample's replicate results was calculated for available results, then grouped by seroprotection status (titer results \>= 1:40 vs \< 1:40). The number of participants with viral shedding (detected by any approved positive RT-PCR test from a NP swab) was calculated for each study day post-challenge (Day 2 to Day 8) and at any time during the entire challenge period within each pre-challenge seroprotection status group.
Number of Participants With Viral Shedding in NP Swab at Day 5 by Baseline MN Seroprotection Status	Day 5	Blood samples were collected pre-challenge (Day -2) for the MN assay conducted with the A/Bethesda/MM2/H1N1 virus as the antigen. The geometric mean of each sample's replicate results was calculated for available results, then grouped by seroprotection status (titer results \>= 1:40 vs \< 1:40). The number of participants with viral shedding (detected by any approved positive RT-PCR test from a NP swab) was calculated for each study day post-challenge (Day 2 to Day 8) and at any time during the entire challenge period within each pre-challenge seroprotection status group.
Number of Participants With Viral Shedding in NP Swab at Day 6 by Baseline MN Seroprotection Status	Day 6	Blood samples were collected pre-challenge (Day -2) for the MN assay conducted with the A/Bethesda/MM2/H1N1 virus as the antigen. The geometric mean of each sample's replicate results was calculated for available results, then grouped by seroprotection status (titer results \>= 1:40 vs \< 1:40). The number of participants with viral shedding (detected by any approved positive RT-PCR test from a NP swab) was calculated for each study day post-challenge (Day 2 to Day 8) and at any time during the entire challenge period within each pre-challenge seroprotection status group.
Number of Participants With Viral Shedding in NP Swab at Day 7 by Baseline MN Seroprotection Status	Day 7	Blood samples were collected pre-challenge (Day -2) for the MN assay conducted with the A/Bethesda/MM2/H1N1 virus as the antigen. The geometric mean of each sample's replicate results was calculated for available results, then grouped by seroprotection status (titer results \>= 1:40 vs \< 1:40). The number of participants with viral shedding (detected by any approved positive RT-PCR test from a NP swab) was calculated for each study day post-challenge (Day 2 to Day 8) and at any time during the entire challenge period within each pre-challenge seroprotection status group.
Number of Participants With Viral Shedding in NP Swab at Day 8 by Baseline MN Seroprotection Status	Day 8	Blood samples were collected pre-challenge (Day -2) for the MN assay conducted with the A/Bethesda/MM2/H1N1 virus as the antigen. The geometric mean of each sample's replicate results was calculated for available results, then grouped by seroprotection status (titer results \>= 1:40 vs \< 1:40). The number of participants with viral shedding (detected by any approved positive RT-PCR test from a NP swab) was calculated for each study day post-challenge (Day 2 to Day 8) and at any time during the entire challenge period within each pre-challenge seroprotection status group.
Number of Participants With Viral Shedding in NP Swab Anytime Post-challenge by Baseline MN Seroprotection Status	Day 2 through Day 8	Blood samples were collected pre-challenge (Day -2) for the HAI assay conducted with the A/Bethesda/MM2/H1N1 virus as the antigen. The geometric mean of each sample's replicate results was calculated for available results, then grouped by seroprotection status (titer results \>= 1:40 vs \< 1:40). The number of participants with viral shedding (detected by any approved positive RT-PCR test from a NP swab) was calculated for each study day post-challenge (Day 2 to Day 8) and at any time during the entire challenge period within each pre-challenge seroprotection status group.
Time Until Detectable Viral Shedding in NP Swab by Baseline HAI Seroprotection Status	Day 2 through Day 8	Blood samples were collected pre-challenge (Day -2) for the HAI assay conducted with the A/Bethesda/MM2/H1N1 virus as the antigen. The geometric mean of each sample's replicate results was calculated from available results, then grouped by seroprotection status (titer results \>= 1:40 vs \< 1:40). Time until viral shedding (detected by any approved positive RT-PCR test from a NP swab) was calculated as the initial day of viral shedding post-challenge for each participant. Median time to viral shedding was calculated within each pre-challenge seroprotection status group via the Kaplan-Meier estimator.
Time Until Detectable Viral Shedding in NP Swab by Baseline MN Seroprotection Status	Day 2 through Day 8	Blood samples were collected pre-challenge (Day -2) for the MN assay conducted with the A/Bethesda/MM2/H1N1 virus as the antigen. The geometric mean of each sample's replicate results was calculated from available results, then grouped by seroprotection status (titer results \>= 1:40 vs \< 1:40). Time until viral shedding (detected by any approved positive RT-PCR test from a NP swab) was calculated as the initial day of viral shedding post-challenge for each participant. Median time to viral shedding was calculated within each pre-challenge seroprotection status group via the Kaplan-Meier estimator.
Magnitude of Viral Shedding in NP Swab by Baseline HAI Seroprotection Status	Day 2 through Day 15	Blood samples were collected pre-challenge (Day -2) for the HAI assay conducted with the A/Bethesda/MM2/H1N1 virus as the antigen. The geometric mean of each sample's replicate results was calculated from available results, then grouped by seroprotection status (titer results \>= 1:40 vs \< 1:40). The quantity of viral load copies/mL from NP swab was measured via quantitative RT-PCR result for each post-challenge study day. The mean of each sample's quantitative PCR replicate results was calculated from available results. Total viral shedding, as observed until study discharge, was calculated as the area under the curve (AUC), then log-10 transformed. Peak viral shedding was calculated as the maximum viral load copies/mL observed until study discharge, then log-10 transformed. The mean and median of the log-10 AUC and the mean and median of the log-10 peak viral load were both calculated within each pre-challenge seroprotection status group.
Magnitude of Viral Shedding in NP Swab by Baseline MN Seroprotection Status	Day 2 through Day 15	Blood samples were collected pre-challenge (Day -2) for the MN assay conducted with the A/Bethesda/MM2/H1N1 virus as the antigen. The geometric mean of each sample's replicate results was calculated from available results, then grouped by seroprotection status (titer results \>= 1:40 vs \< 1:40). The quantity of viral load copies/mL from NP swab was measured via quantitative RT-PCR result for each post-challenge study day. The mean of each sample's quantitative PCR replicate results was calculated from available results. Total viral shedding, as observed until study discharge, was calculated as the area under the curve (AUC), then log-10 transformed. Peak viral shedding was calculated as the maximum viral load copies/mL observed until study discharge, then log-10 transformed. The mean and median of the log-10 AUC and the mean and median of the log-10 peak viral load were both calculated within each pre-challenge seroprotection status group.
GMT of HAI Antibody in Serum at Day 29 by Infection Status	Day 29	Blood samples were collected pre-challenge (Day -2) and post-challenge on Days 8, 29 and 61 for the HAI assay conducted with the A/Bethesda/MM2/H1N1 virus as the antigen. The geometric mean of each sample's replicate results was calculated from available results. The geometric mean across samples was calculated within each study day and by infection status as observed over the study challenge period (Day 2 to Day 8); RT-PCR Negative (never positive), RT-PCR Positive Asymptomatic (participants with at least one positive PCR result but no symptoms reported), at least once RT-PCR Positive Symptomatic (or MMID).
Percentage of Participants Reporting Any MMID Symptom During Challenge Period by Viral Shedding Status and Baseline HAI Seroprotection Status From Serum Measured at Baseline With RT-PCR Negative (None Positive)	Day 2 through Day 8	Blood samples were collected pre-challenge (Day -2) for the HAI assay conducted with the A/Bethesda/MM2/H1N1 virus as the antigen. The geometric mean of each sample's replicate results was calculated from available results, then grouped by seroprotection status (titer results \>= 1:40 vs \< 1:40). The presence of any of the following symptoms was assessed from Day 2 to Day 8; body aches or pain, chest tightness, chills, conjunctivitis, nasal congestion, sinus congestion, coryza, decreased appetite, diarrhea, dry cough, dyspnea, fatigue, fever, headache, lymphopenia, nausea, a 3% or more decrease in oxygen saturation from baseline, productive cough, rhinorrhea, sore throat, and sweats. The percentage of participants that reported any symptom was calculated within each pre-challenge seroprotection status group and by viral shedding status, as observed anytime from Day 2 to Day 8; RT-PCR Negative (never positive), and at least once RT-PCR Positive.
Number of Serious Adverse Events (SAE) Post-challenge Through the Inpatient Stay	Day 1 through Day 8	SAEs included any untoward medical occurrence that resulted in death or a congenital anomaly/birth defect; was life threatening or a persistent/significant disability/incapacity; required inpatient hospitalization or prolongation of existing hospitalization. All events are included regardless of relationship to the study challenge.
Number of Serious Adverse Events (SAE) Post- Inpatient Discharge Through the Duration of the Study	Day 9 through Day 91	SAEs included any untoward medical occurrence that resulted in death or a congenital anomaly/birth defect; was life threatening or a persistent/significant disability/incapacity; required inpatient hospitalization or prolongation of existing hospitalization. All events are included regardless of relationship to the study challenge.This table provides the number and percentage of participants who reported SAEs following discharge from the study hospital.
Percentage of Participants Reporting Any MMID Symptom During Challenge Period by Viral Shedding Status and Baseline HAI Seroprotection Status From Serum Measured at Baseline - RT-PCR Positive (One or More)	Day 2 through Day 8	Blood samples were collected pre-challenge (Day -2) for the HAI assay conducted with the A/Bethesda/MM2/H1N1 virus as the antigen. The geometric mean of each sample's replicate results was calculated from available results, then grouped by seroprotection status (titer results \>= 1:40 vs \< 1:40). The presence of any of the following symptoms was assessed from Day 2 to Day 8; body aches or pain, chest tightness, chills, conjunctivitis, nasal congestion, sinus congestion, coryza, decreased appetite, diarrhea, dry cough, dyspnea, fatigue, fever, headache, lymphopenia, nausea, a 3% or more decrease in oxygen saturation from baseline, productive cough, rhinorrhea, sore throat, and sweats. The percentage of participants that reported any symptom was calculated within each pre-challenge seroprotection status group and by viral shedding status, as observed anytime from Day 2 to Day 8; RT-PCR Negative (never positive), and at least once RT-PCR Positive.
Geometric Mean Titer (GMT) of HAI Antibody in Serum at Baseline by Infection Status	Day -2	Blood samples were collected pre-challenge (Day -2) and post-challenge on Days 8, 29 and 61 for the HAI assay conducted with the A/Bethesda/MM2/H1N1 virus as the antigen. The geometric mean of each sample's replicate results was calculated from available results. The geometric mean across samples was calculated within each study day and by infection status as observed over the study challenge period (Day 2 to Day 8); RT-PCR Negative (never positive), RT-PCR Positive Asymptomatic (participants with at least one positive PCR result but no symptoms reported), at least once RT-PCR Positive Symptomatic (or MMID).

Countries

United States

Participant flow

Recruitment details

Healthy adults, male and female, between the ages of 18 and 49, who are non-habitual smokers without medical conditions at high risk for severe complications of influenza virus infection were enrolled. Participants were enrolled between 22OCT2019 and 05DEC2019.

Participants by arm

Arm	Count
Study Group Participants will receive 2 mL (approximately 5x10\^6/mL tissue culture infective dose (TCID50)) of influenza A/Bethesda/MM2/H1N1challenge virus administered intranasally via a sprayer on Day 1.	76
Total	76

Withdrawals & dropouts

Period	Reason	FG000
Overall Study	Lost to Follow-up	9
Overall Study	Withdrawal by Subject	2

Baseline characteristics

Characteristic	Study Group
Age, Categorical <=18 years	0 Participants
Age, Categorical >=65 years	0 Participants
Age, Categorical Between 18 and 65 years	76 Participants
Age, Continuous	33.4 years STANDARD_DEVIATION 9.2
Baseline Seroprotection (Hemagglutination Inhibition) High >= 1:40	37 Participants
Baseline Seroprotection (Hemagglutination Inhibition) Low < 1:40	39 Participants
Baseline Seroprotection (Microneutralization) High >= 1:40	53 Participants
Baseline Seroprotection (Microneutralization) Low < 1:40	23 Participants
Ethnicity (NIH/OMB) Hispanic or Latino	5 Participants
Ethnicity (NIH/OMB) Not Hispanic or Latino	71 Participants
Ethnicity (NIH/OMB) Unknown or Not Reported	0 Participants
Race (NIH/OMB) American Indian or Alaska Native	1 Participants
Race (NIH/OMB) Asian	1 Participants
Race (NIH/OMB) Black or African American	35 Participants
Race (NIH/OMB) More than one race	3 Participants
Race (NIH/OMB) Native Hawaiian or Other Pacific Islander	0 Participants
Race (NIH/OMB) Unknown or Not Reported	2 Participants
Race (NIH/OMB) White	34 Participants
Receipt of Prior Non-Seasonal Influenza Vaccination (2018-2019) No	73 Participants
Receipt of Prior Non-Seasonal Influenza Vaccination (2018-2019) Yes	3 Participants
Receipt of Prior Seasonal Influenza Vaccination (2018-2019) No	67 Participants
Receipt of Prior Seasonal Influenza Vaccination (2018-2019) Yes	9 Participants
Region of Enrollment United States Cincinnati Children's Hospital	24 Participants
Region of Enrollment United States Duke University	15 Participants
Region of Enrollment United States Saint Louis University	17 Participants
Region of Enrollment United States University of Maryland	20 Participants
Region of Enrollment United States	76 Participants
Sex: Female, Male Female	30 Participants
Sex: Female, Male Male	46 Participants

Adverse events

Event type	EG000 affected / at risk
deaths Total, all-cause mortality	0 / 76
other Total, other adverse events	41 / 76
serious Total, serious adverse events	0 / 76

Outcome results

Primary

Association Between Clinical or Laboratory Manifestation of MMID and A/Bethesda/MM2/H1N1 HAI Antibodies in Serum at Baseline

Blood samples were collected pre-challenge (Day -2) for the HAI assay conducted with the A/Bethesda/MM2/H1N1 virus as the antigen. The geometric mean of each sample's replicate results was calculated from available results. MMID is a composite endpoint determined by the presence of viral shedding (detected by any approved positive RT-PCR test from a NP swab), accompanied by at least one the following symptoms occurring any time from Day 2 through Day 8; body aches or pain, chest tightness, chills, conjunctivitis, nasal congestion, sinus congestion, coryza, decreased appetite, diarrhea, dry cough, dyspnea, fatigue, fever, headache, lymphopenia, nausea, a 3% or more decrease in oxygen saturation from baseline, productive cough, rhinorrhea, sore throat, and sweats. The relationship between the level of pre-challenge HAI titer and the likelihood of developing MMID during the study challenge period (Day 2 to Day 8) was assessed via logistic regression.

Time frame: Day 2 to Day 8

Population: All participants who received the study challenge, had a baseline sample for immunogenicity, and were followed for the entire duration of the study challenge period, or at least until MMID was observed.

Arm	Measure	Value (NUMBER)
Study Group	Association Between Clinical or Laboratory Manifestation of MMID and A/Bethesda/MM2/H1N1 HAI Antibodies in Serum at Baseline	0.81 Odds Ratio

Comparison: Pre-challenge (baseline) HAI geometric mean titer was log-2 transformed and treated as a continuous variable in the model.p-value: 0.12695% CI: [0.62, 1.06]Wald Chi-Square

Primary

Percentage of Healthy Participants Reporting Mild-to-Moderate Influenza Disease (MMID) by Baseline A/Bethesda/MM2/H1N1 Hemagglutination Inhibition (HAI) Antibody Seroprotection Status (Titer >/= 1:40 vs. Titer < 1:40)

Blood samples were collected pre-challenge (Day -2) for the HAI assay conducted with the A/Bethesda/MM2/H1N1 virus as the antigen. The geometric mean of each sample's replicate results was calculated from available results, then grouped by seroprotection status (titer results \>= 1:40 vs \< 1:40). MMID is a composite endpoint determined by the presence of viral shedding (detected by any approved positive RT-PCR test from a NP swab), accompanied by at least one the following symptoms occurring any time from Day 2 through Day 8; body aches or pain, chest tightness, chills, conjunctivitis, nasal congestion, sinus congestion, coryza, decreased appetite, diarrhea, dry cough, dyspnea, fatigue, fever, headache, lymphopenia, nausea, a 3% or more decrease in oxygen saturation from baseline, productive cough, rhinorrhea, sore throat, and sweats. The percentage of participants that developed MMID was calculated within each pre-challenge seroprotection status group.

Time frame: Day 2 through Day 8

Arm	Measure	Group	Value (NUMBER)
Study Group	Percentage of Healthy Participants Reporting Mild-to-Moderate Influenza Disease (MMID) by Baseline A/Bethesda/MM2/H1N1 Hemagglutination Inhibition (HAI) Antibody Seroprotection Status (Titer >/= 1:40 vs. Titer < 1:40)	Baseline Seroprotection Status Low < 1:40 : MMID	77 percentage of participants
Study Group	Percentage of Healthy Participants Reporting Mild-to-Moderate Influenza Disease (MMID) by Baseline A/Bethesda/MM2/H1N1 Hemagglutination Inhibition (HAI) Antibody Seroprotection Status (Titer >/= 1:40 vs. Titer < 1:40)	Baseline Seroprotection Status Low < 1:40 : No MMID	23 percentage of participants
Study Group	Percentage of Healthy Participants Reporting Mild-to-Moderate Influenza Disease (MMID) by Baseline A/Bethesda/MM2/H1N1 Hemagglutination Inhibition (HAI) Antibody Seroprotection Status (Titer >/= 1:40 vs. Titer < 1:40)	Baseline Seroprotection Status High > = 1:40 : No MMID	35 percentage of participants
Study Group	Percentage of Healthy Participants Reporting Mild-to-Moderate Influenza Disease (MMID) by Baseline A/Bethesda/MM2/H1N1 Hemagglutination Inhibition (HAI) Antibody Seroprotection Status (Titer >/= 1:40 vs. Titer < 1:40)	Baseline Seroprotection Status High > = 1:40 : MMID	65 percentage of participants

Secondary

Duration of Viral Shedding in Nasopharyngeal (NP) Swab by Baseline HAI Seroprotection Status

Blood samples were collected pre-challenge (Day -2) for the HAI assay conducted with the A/Bethesda/MM2/H1N1 virus as the antigen. The geometric mean of each sample's replicate results was calculated from available results, then grouped by seroprotection status (titer results \>= 1:40 vs \< 1:40). Duration of viral shedding (detected by any approved positive RT-PCR test from NP swab) was calculated from the day of the initial positive PCR result to the day of the last positive PCR result prior to discharge from the challenge unit facility, regardless of intermittent negative PCR results. The mean duration of viral shedding was calculated among participants with detected virus within each pre-challenge HAI seroprotection status group.

Time frame: Day 2 through Day 15

Population: All participants who received the study challenge, had a baseline sample for immunogenicity, and were followed for the entire duration of the study challenge period.

Arm	Measure	Group	Value (MEAN)
Study Group	Duration of Viral Shedding in Nasopharyngeal (NP) Swab by Baseline HAI Seroprotection Status	Low < 1:40	3.8 days
Study Group	Duration of Viral Shedding in Nasopharyngeal (NP) Swab by Baseline HAI Seroprotection Status	High >= 1:40	2.3 days

Secondary

Duration of Viral Shedding in NP Swab by Baseline MN Seroprotection Status

Blood samples were collected pre-challenge (Day -2) for the MN assay conducted with the A/Bethesda/MM2/H1N1 virus as the antigen. The geometric mean of each sample's replicate results was calculated from available results, then grouped by seroprotection status (titer results \>= 1:40 vs \< 1:40). Duration of viral shedding (detected by any approved positive RT-PCR test from NP swab) was calculated from the day of the initial positive PCR result to the day of the last positive PCR result prior to discharge from the challenge unit facility, regardless of intermittent negative PCR results. The mean duration of viral shedding was calculated among participants with detected virus within each pre-challenge MN seroprotection status group.

Time frame: Day 2 to Day 15

Population: All participants who received the study challenge, had a baseline sample for immunogenicity, and were followed for the entire duration of the study challenge period.

Arm	Measure	Group	Value (MEAN)
Study Group	Duration of Viral Shedding in NP Swab by Baseline MN Seroprotection Status	Low < 1:40	3.9 Days
Study Group	Duration of Viral Shedding in NP Swab by Baseline MN Seroprotection Status	High >= 1:40	2.7 Days

Secondary

Geometric Mean Titer (GMT) of HAI Antibody in Serum at Baseline by Infection Status

Blood samples were collected pre-challenge (Day -2) and post-challenge on Days 8, 29 and 61 for the HAI assay conducted with the A/Bethesda/MM2/H1N1 virus as the antigen. The geometric mean of each sample's replicate results was calculated from available results. The geometric mean across samples was calculated within each study day and by infection status as observed over the study challenge period (Day 2 to Day 8); RT-PCR Negative (never positive), RT-PCR Positive Asymptomatic (participants with at least one positive PCR result but no symptoms reported), at least once RT-PCR Positive Symptomatic (or MMID).

Time frame: Day -2

Population: All participants who received the study challenge, had an available immunogenicity sample for the given study day, and were followed for the entire duration of the study challenge period, or at least until MMID was observed.

Arm	Measure	Group	Value (GEOMETRIC_MEAN)
Study Group	Geometric Mean Titer (GMT) of HAI Antibody in Serum at Baseline by Infection Status	RT-PCR Positive Asymptomatic	20.0 titer
Study Group	Geometric Mean Titer (GMT) of HAI Antibody in Serum at Baseline by Infection Status	RT-PCR Negative	117.9 titer
Study Group	Geometric Mean Titer (GMT) of HAI Antibody in Serum at Baseline by Infection Status	RT-PCR Positive Symptomatic	36.8 titer

Secondary

GMT of HAI Antibody in Serum at Day 29 by Infection Status

Time frame: Day 29

Arm	Measure	Group	Value (GEOMETRIC_MEAN)
Study Group	GMT of HAI Antibody in Serum at Day 29 by Infection Status	RT-PCR Positive Asymptomatic	63.9 titer
Study Group	GMT of HAI Antibody in Serum at Day 29 by Infection Status	RT-PCR Negative	126.6 titer
Study Group	GMT of HAI Antibody in Serum at Day 29 by Infection Status	RT-PCR Positive Symptomatic	87.4 titer

Secondary

GMT of HAI Antibody in Serum at Day 61 by Infection Status

Time frame: Day 61

Arm	Measure	Group	Value (GEOMETRIC_MEAN)
Study Group	GMT of HAI Antibody in Serum at Day 61 by Infection Status	RT-PCR Positive Symptomatic	78.0 titer
Study Group	GMT of HAI Antibody in Serum at Day 61 by Infection Status	RT-PCR Negative	123.1 titer
Study Group	GMT of HAI Antibody in Serum at Day 61 by Infection Status	RT-PCR Positive Asymptomatic	71.3 titer

Secondary

GMT of HAI Antibody in Serum at Day 8 by Infection Status

Time frame: Day 8

Arm	Measure	Group	Value (GEOMETRIC_MEAN)
Study Group	GMT of HAI Antibody in Serum at Day 8 by Infection Status	RT-PCR Positive Symptomatic	46.1 titer
Study Group	GMT of HAI Antibody in Serum at Day 8 by Infection Status	RT-PCR Positive Asymptomatic	23.7 titer
Study Group	GMT of HAI Antibody in Serum at Day 8 by Infection Status	RT-PCR Negative	122.5 titer

Secondary

GMT of Microneutralization (MN) Antibody in Serum at Baseline by Infection Status

Blood samples were collected pre-challenge (Day -2) and post-challenge on Days 8, 29 and 61 for the MN assay conducted with the A/Bethesda/MM2/H1N1 virus as the antigen. The geometric mean of each sample's replicate results was calculated from available results. The geometric mean across samples was calculated within each study day and by infection status as observed over the study challenge period (Day 2 to Day 8); RT-PCR Negative (never positive), RT-PCR Positive Asymptomatic (participants with at least one positive PCR result but no symptoms reported), at least once RT-PCR Positive Symptomatic (or MMID).

Time frame: Day -2

Arm	Measure	Group	Value (GEOMETRIC_MEAN)
Study Group	GMT of Microneutralization (MN) Antibody in Serum at Baseline by Infection Status	RT-PCR Positive Symptomatic	62.9 titer
Study Group	GMT of Microneutralization (MN) Antibody in Serum at Baseline by Infection Status	RT-PCR Positive Asymptomatic	44.3 titer
Study Group	GMT of Microneutralization (MN) Antibody in Serum at Baseline by Infection Status	RT-PCR Negative	276.7 titer

Secondary

GMT of MN Antibody in Serum at Day 29 by Infection Status

Time frame: Day 29

Arm	Measure	Group	Value (GEOMETRIC_MEAN)
Study Group	GMT of MN Antibody in Serum at Day 29 by Infection Status	RT-PCR Positive Symptomatic	159.5 titer
Study Group	GMT of MN Antibody in Serum at Day 29 by Infection Status	RT-PCR Positive Asymptomatic	103.1 titer
Study Group	GMT of MN Antibody in Serum at Day 29 by Infection Status	RT-PCR Negative	320.0 titer

Secondary

GMT of MN Antibody in Serum at Day 61 by Infection Status

Time frame: Day 61

Arm	Measure	Group	Value (GEOMETRIC_MEAN)
Study Group	GMT of MN Antibody in Serum at Day 61 by Infection Status	RT-PCR Positive Symptomatic (MMID-1)	151.8 titer
Study Group	GMT of MN Antibody in Serum at Day 61 by Infection Status	RT-PCR Positive Asymptomatic	107.2 titer
Study Group	GMT of MN Antibody in Serum at Day 61 by Infection Status	RT-PCR Negative	287.6 titer

Secondary

GMT of MN Antibody in Serum at Day 8 by Infection Status

Time frame: Day 8

Arm	Measure	Group	Value (GEOMETRIC_MEAN)
Study Group	GMT of MN Antibody in Serum at Day 8 by Infection Status	RT-PCR Positive Symptomatic	87.7 titer
Study Group	GMT of MN Antibody in Serum at Day 8 by Infection Status	RT-PCR Positive Asymptomatic	52.4 titer
Study Group	GMT of MN Antibody in Serum at Day 8 by Infection Status	RT-PCR Negative	250.6 titer

Secondary

Magnitude of Viral Shedding in NP Swab by Baseline HAI Seroprotection Status

Blood samples were collected pre-challenge (Day -2) for the HAI assay conducted with the A/Bethesda/MM2/H1N1 virus as the antigen. The geometric mean of each sample's replicate results was calculated from available results, then grouped by seroprotection status (titer results \>= 1:40 vs \< 1:40). The quantity of viral load copies/mL from NP swab was measured via quantitative RT-PCR result for each post-challenge study day. The mean of each sample's quantitative PCR replicate results was calculated from available results. Total viral shedding, as observed until study discharge, was calculated as the area under the curve (AUC), then log-10 transformed. Peak viral shedding was calculated as the maximum viral load copies/mL observed until study discharge, then log-10 transformed. The mean and median of the log-10 AUC and the mean and median of the log-10 peak viral load were both calculated within each pre-challenge seroprotection status group.

Time frame: Day 2 through Day 15

Population: All participants who received the study challenge, had a baseline sample for immunogenicity, were followed for the entire duration of the study challenge period,.

Arm	Measure	Group	Value (MEAN)
Study Group	Magnitude of Viral Shedding in NP Swab by Baseline HAI Seroprotection Status	AUC - Low < 1:40	4.7 log-10 copies/mL
Study Group	Magnitude of Viral Shedding in NP Swab by Baseline HAI Seroprotection Status	AUC - High >= 1:40	1.8 log-10 copies/mL
Study Group	Magnitude of Viral Shedding in NP Swab by Baseline HAI Seroprotection Status	Peak viral load - Low < 1:40	4.7 log-10 copies/mL
Study Group	Magnitude of Viral Shedding in NP Swab by Baseline HAI Seroprotection Status	Peak viral load - High >= 1:40	2.1 log-10 copies/mL

Secondary

Magnitude of Viral Shedding in NP Swab by Baseline MN Seroprotection Status

Blood samples were collected pre-challenge (Day -2) for the MN assay conducted with the A/Bethesda/MM2/H1N1 virus as the antigen. The geometric mean of each sample's replicate results was calculated from available results, then grouped by seroprotection status (titer results \>= 1:40 vs \< 1:40). The quantity of viral load copies/mL from NP swab was measured via quantitative RT-PCR result for each post-challenge study day. The mean of each sample's quantitative PCR replicate results was calculated from available results. Total viral shedding, as observed until study discharge, was calculated as the area under the curve (AUC), then log-10 transformed. Peak viral shedding was calculated as the maximum viral load copies/mL observed until study discharge, then log-10 transformed. The mean and median of the log-10 AUC and the mean and median of the log-10 peak viral load were both calculated within each pre-challenge seroprotection status group.

Time frame: Day 2 through Day 15

Population: All participants who received the study challenge, had a baseline sample for immunogenicity, and were followed for the entire duration of the study challenge period.

Arm	Measure	Group	Value (MEAN)
Study Group	Magnitude of Viral Shedding in NP Swab by Baseline MN Seroprotection Status	Peak viral load - Low < 1:40	4.7 log-10 copies/mL
Study Group	Magnitude of Viral Shedding in NP Swab by Baseline MN Seroprotection Status	Peak viral load - High >= 1:40	2.9 log-10 copies/mL
Study Group	Magnitude of Viral Shedding in NP Swab by Baseline MN Seroprotection Status	AUC - Low < 1:40	4.6 log-10 copies/mL
Study Group	Magnitude of Viral Shedding in NP Swab by Baseline MN Seroprotection Status	AUC - High >= 1:40	2.7 log-10 copies/mL

Secondary