The time from the first administration of IMP to the first confirmed negative qRT-PCR test after the peak qRT-PCR measurement was calculated as: Date and time of first confirmed negative test after peak qRT-PCR measurement minus Date and time of first IMP administration. A negative test was defined as two consecutive 'Not Detected' results in the qRT-PCR test. The peak qRT-PCR was defined as the highest viral load value obtained by a participant after their first administration of IMP. Participants without a confirmed undetectable assessment after their peak, were censored at their last detected qRT-PCR assessment.

The time from the peak qRT-PCR measurement after administration of IMP to the first confirmed negative qRT-PCR test was calculated as (Date and time of first confirmed negative test after peak qRT-PCR measurement minus Date and time of peak qRT-PCR measurement). A negative test was defined as two consecutive 'Not Detected' results in the qRT-PCR test. The peak qRT-PCR was defined as the highest viral load value obtained by a participant after their first administration of IMP. Participants without a confirmed undetectable assessment after their peak, were censored at their last detected qRT-PCR assessment.

The time to the peak qRT-PCR measurement starting from the initial administration of IMP was calculated as: Date and time of peak qRT-PCR measurement minus Date and time of first IMP administration. The peak qRT-PCR was defined as the highest viral load value obtained by a participant after their first administration of IMP.

Area under the viral load-time curve (VL-AUC) of RSV challenge virus as determined by viral culture on nasal samples, starting at initial administration of IMP up to planned discharge from quarantine was reported in this outcome measure.

Peak viral load of RSV as defined by the maximum viral load determined by viral culture measurements in nasal samples starting from initial administration of IMP up to planned discharge from quarantine was reported in this outcome measure.

Time to confirmed negative test by viral culture measurements in nasal samples from initial administration of IMP up to first confirmed negative viral culture measurement after the peak viral culture measurement was calculated as: Date and time of first confirmed negative test after peak viral culture measurement minus Date and time of first IMP administration. A negative test was defined as two consecutive 'Not Detected' results in the viral culture test. The peak viral culture measurement was defined as the highest viral load value obtained by a participant after their first administration of IMP. Participants who did not have a confirmed undetectable assessment after their peak viral culture measurement after first administration of IMP were censored at their last detectable assessment.

The time from the peak viral culture measurement after administration of IMP to the first confirmed negative viral culture measurement was calculated in days as: Date of and time first confirmed negative test minus Date and time of peak qRT-PCR measurement. A negative test was defined as two consecutive 'Not Detected' results in the viral culture test. The peak viral culture measurement was defined as the highest viral load value obtained by a participant after their first administration of IMP. Participants who did not have a confirmed undetectable assessment after their peak viral culture measurement after first administration of IMP were censored at their last detectable assessment.

Area under the Curve over Time of Total Clinical Symptoms (TSS-AUC) as measured from 10 symptoms within Graded Symptom Scoring System Collected 3 Times Daily Starting at Initial Administration up to Planned Discharge from Quarantine. TSS (from 10 items of the 13-item symptom diary card) was used to calculate the AUC, from the assessment nearest to the time of the first administration of IMP until Day 12. Following types of symptoms were recorded on symptom diary cards: Upper Respiratory Tract (URT): runny nose, stuffy nose, sore throat, sneezing, earache; Lower Respiratory Tract (LRT): cough, shortness of breath; Systemic: headache, malaise, muscle/joint ache/stiffness. Each symptom was recorded on a grading scale of 0 to 3 (or 0 to 4 for the Shortness of Breath symptom), higher scores = greater severity of symptoms. Total symptom score was calculated as sum of the 10 observed symptom grade values and ranged from 0 to 31, where higher scores indicated more severe symptoms.

Area under the curve over time of total clinical symptoms change from baseline (TSS-AUC-CFB) as measured from 10 symptoms within the graded symptom scoring system collected 3 times daily starting at initial administration of IMP up to planned discharge from quarantine (Day 12, am). The following types of symptoms were recorded: Upper Respiratory Tract (URT): runny nose, stuffy nose, sore throat, sneezing, earache; Lower Respiratory Tract (LRT): cough, shortness of breath; Systemic: headache, malaise, muscle/joint ache/stiffness. Each symptom was recorded on a grading scale of 0 to 3 (or 0 to 4 for the Shortness of Breath symptom), where higher scores indicated greater severity of symptoms. TSS was calculated as sum of the 10 observed symptom grade values and ranged from 0 to 31, where higher scores indicated more severe symptoms. The AUC calculation was based on the available non-missing calculated total symptom scores between the start and end of the defined AUC time.

Peak total clinical symptoms (TSS) as measured from 10 symptoms within the graded symptom scoring system collected 3 times daily starting from initial administration of IMP up to planned discharge from quarantine. The following types of symptoms were recorded: Upper Respiratory Tract (URT): runny nose, stuffy nose, sore throat, sneezing, earache; Lower Respiratory Tract (LRT): cough, shortness of breath; Systemic: headache, malaise, muscle/joint ache/stiffness. Each symptom was recorded on a grading scale of 0 to 3 (or 0 to 4 for the Shortness of Breath symptom), where higher scores indicated greater severity of symptoms. The total symptom score was calculated as sum of the 10 observed symptom grade values and ranged from 0 to 31, where higher scores indicated more severe symptoms. The overall peak score was defined as the highest scoring symptom diary card observed from the first administration of IMP until quarantine discharge.

Individual maximum daily sum of symptom score from initial administration of IMP up to planned discharge from quarantine. The following types of symptoms were recorded: Upper Respiratory Tract (URT): runny nose, stuffy nose, sore throat, sneezing, earache; Lower Respiratory Tract (LRT): cough, shortness of breath; Systemic: headache, malaise, muscle/joint ache/stiffness. Each symptom was recorded on a grading scale of 0 to 3 (or 0 to 4 for the Shortness of Breath symptom), where higher scores indicated greater severity of symptoms. The total symptom score was calculated as sum of the 10 observed symptom grade values and ranged from 0 to 31, where higher scores indicated more severe symptoms. The highest total symptom score recorded on each day, across the three assessments was reported in this outcome measure. The peak daily score was defined as the highest scoring symptom diary card observed on each day from the first administration of IMP until quarantine discharge.

Symptom resolution was defined as a participant scoring 0 for the total symptom score for a 24-hour period (e.g., a minimum of three consecutive symptom diary cards, each with a score of 0) after their peak symptom score. The time from the assessment at the time of the first administration of IMP until symptom resolution was calculated as: Date and time of symptom resolution minus Date and time of assessment at IMP administration. If the peak symptom score occurred on more than one day then the first occurrence was selected. Participants who did not record 24 hours symptom free after their highest total symptom score during the quarantine period were censored at their last assessment.

Symptom resolution was defined as a participant scoring 0 for the total symptom score for a 24-hour period (e.g., a minimum of three consecutive symptom diary cards, each with a score of 0) after their peak symptom score. The time from the highest total symptom score following administration of IMP until symptom resolution was calculated as: Date and time of symptom resolution minus Date and time of highest total symptom score. If the peak symptom score occurred on more than one day then the first occurrence was selected. Participants who did not record 24 hours symptom free after their highest total symptom score during the quarantine period were censored at their last assessment.

Time to peak as measured from 10 symptoms within the graded daily symptom scoring system starting from initial administration of IMP to the time of peak daily symptom score. If the peak symptom score occurred on more than one day then the first occurrence was selected. Participants were censored at their last assessment if they did not record any symptoms during the quarantine period.

Total weight of nasal mucus was calculated as the sum of mucus weights taken from the assessment at the time of the first administration of IMP (prior to or after dosing, depending on whether dosed in the morning or evening) to morning of Day 12 (Quarantine discharge).

Total number of tissues was counted from the assessment at the time of the first dose of IMP (prior to or after dosing, depending on whether dosed in the morning or evening) to morning of Day 12 (Quarantine discharge).

An adverse event was defined as any untoward medical occurrence in clinical study participants administered a pharmaceutical product. An AE did not necessarily have a causal relationship with the study intervention. An SAE was defined as any untoward medical occurrence that, at any dose: resulted in death, was life threatening, required inpatient hospitalization or prolongation of existing hospitalization, resulted in persistent disability/incapacity, was a congenital anomaly/birth defect or important medical event.

An Adverse Event was defined as any untoward medical occurrence in clinical study participants administered a pharmaceutical product. An AE did not necessarily have a causal relationship with the study intervention. Number of participants with AEs possibly, probably or definitely related to viral challenge agents were reported by preferred terms in this outcome measure.

Number of participants with concomitant medications were reported in this outcome measure.

Area under the plasma concentration-time curve from time zero to the end of the dosing interval for RV299 where dosing interval=12 hours.

Total of all reporting groups

Participants were administered an oral suspension of placebo twice daily at an interval of approximately 12 hours for 5 consecutive days from Day 2 following confirmation of RSV infection. Participants without a positive result for RSV infection were administered placebo from Day 5.

Peak viral load of RSV as defined by the maximum viral load determined by qRT-PCR measurements in nasal samples starting from initial administration of IMP up to planned discharge from quarantine was reported in this outcome measure.

ITT-I Population consisted of all randomized participants who received challenge virus and at least 1 dose of IMP and met the criterion for RSV infection.

The time from the first administration of IMP to the first confirmed negative qRT-PCR test after the peak qRT-PCR measurement was calculated as: Date and time of first confirmed negative test after peak qRT-PCR measurement minus Date and time of first IMP administration. A negative test was defined as two consecutive 'Not Detected' results in the qRT-PCR test. The peak qRT-PCR was defined as the highest viral load value obtained by a participant after their first administration of IMP. Participants without a confirmed undetectable assessment after their peak, were censored at their last detected qRT-PCR assessment.

ITT-I Population consisted of all randomized participants who received challenge virus and at least 1 dose of IMP and met the criterion for RSV infection.

The time from the peak qRT-PCR measurement after administration of IMP to the first confirmed negative qRT-PCR test was calculated as (Date and time of first confirmed negative test after peak qRT-PCR measurement minus Date and time of peak qRT-PCR measurement). A negative test was defined as two consecutive 'Not Detected' results in the qRT-PCR test. The peak qRT-PCR was defined as the highest viral load value obtained by a participant after their first administration of IMP. Participants without a confirmed undetectable assessment after their peak, were censored at their last detected qRT-PCR assessment.

ITT-I Population consisted of all randomized participants who received challenge virus and at least 1 dose of IMP and met the criterion for RSV infection.

The time to the peak qRT-PCR measurement starting from the initial administration of IMP was calculated as: Date and time of peak qRT-PCR measurement minus Date and time of first IMP administration. The peak qRT-PCR was defined as the highest viral load value obtained by a participant after their first administration of IMP.

ITT-I Population consisted of all randomized participants who received challenge virus and at least 1 dose of IMP and met the criterion for RSV infection.

Area under the viral load-time curve (VL-AUC) of RSV challenge virus as determined by viral culture on nasal samples, starting at initial administration of IMP up to planned discharge from quarantine was reported in this outcome measure.

ITT-I Population consisted of all randomized participants who received challenge virus and at least 1 dose of IMP and met the criterion for RSV infection.

Peak viral load of RSV as defined by the maximum viral load determined by viral culture measurements in nasal samples starting from initial administration of IMP up to planned discharge from quarantine was reported in this outcome measure.

ITT-I Population consisted of all randomized participants who received challenge virus and at least 1 dose of IMP and met the criterion for RSV infection.

Time to confirmed negative test by viral culture measurements in nasal samples from initial administration of IMP up to first confirmed negative viral culture measurement after the peak viral culture measurement was calculated as: Date and time of first confirmed negative test after peak viral culture measurement minus Date and time of first IMP administration. A negative test was defined as two consecutive 'Not Detected' results in the viral culture test. The peak viral culture measurement was defined as the highest viral load value obtained by a participant after their first administration of IMP. Participants who did not have a confirmed undetectable assessment after their peak viral culture measurement after first administration of IMP were censored at their last detectable assessment.

ITT-I Population consisted of all randomized participants who received challenge virus and at least 1 dose of IMP and met the criterion for RSV infection.

The time from the peak viral culture measurement after administration of IMP to the first confirmed negative viral culture measurement was calculated in days as: Date of and time first confirmed negative test minus Date and time of peak qRT-PCR measurement. A negative test was defined as two consecutive 'Not Detected' results in the viral culture test. The peak viral culture measurement was defined as the highest viral load value obtained by a participant after their first administration of IMP. Participants who did not have a confirmed undetectable assessment after their peak viral culture measurement after first administration of IMP were censored at their last detectable assessment.

ITT-I Population consisted of all randomized participants who received challenge virus and at least 1 dose of IMP and met the criterion for RSV infection.

Area under the Curve over Time of Total Clinical Symptoms (TSS-AUC) as measured from 10 symptoms within Graded Symptom Scoring System Collected 3 Times Daily Starting at Initial Administration up to Planned Discharge from Quarantine. TSS (from 10 items of the 13-item symptom diary card) was used to calculate the AUC, from the assessment nearest to the time of the first administration of IMP until Day 12. Following types of symptoms were recorded on symptom diary cards: Upper Respiratory Tract (URT): runny nose, stuffy nose, sore throat, sneezing, earache; Lower Respiratory Tract (LRT): cough, shortness of breath; Systemic: headache, malaise, muscle/joint ache/stiffness. Each symptom was recorded on a grading scale of 0 to 3 (or 0 to 4 for the Shortness of Breath symptom), higher scores = greater severity of symptoms. Total symptom score was calculated as sum of the 10 observed symptom grade values and ranged from 0 to 31, where higher scores indicated more severe symptoms.

ITT-I Population consisted of all randomized participants who received challenge virus and at least 1 dose of IMP and met the criterion for RSV infection.

Area under the curve over time of total clinical symptoms change from baseline (TSS-AUC-CFB) as measured from 10 symptoms within the graded symptom scoring system collected 3 times daily starting at initial administration of IMP up to planned discharge from quarantine (Day 12, am). The following types of symptoms were recorded: Upper Respiratory Tract (URT): runny nose, stuffy nose, sore throat, sneezing, earache; Lower Respiratory Tract (LRT): cough, shortness of breath; Systemic: headache, malaise, muscle/joint ache/stiffness. Each symptom was recorded on a grading scale of 0 to 3 (or 0 to 4 for the Shortness of Breath symptom), where higher scores indicated greater severity of symptoms. TSS was calculated as sum of the 10 observed symptom grade values and ranged from 0 to 31, where higher scores indicated more severe symptoms. The AUC calculation was based on the available non-missing calculated total symptom scores between the start and end of the defined AUC time.

ITT-I Population consisted of all randomized participants who received challenge virus and at least 1 dose of IMP and met the criterion for RSV infection.

Peak total clinical symptoms (TSS) as measured from 10 symptoms within the graded symptom scoring system collected 3 times daily starting from initial administration of IMP up to planned discharge from quarantine. The following types of symptoms were recorded: Upper Respiratory Tract (URT): runny nose, stuffy nose, sore throat, sneezing, earache; Lower Respiratory Tract (LRT): cough, shortness of breath; Systemic: headache, malaise, muscle/joint ache/stiffness. Each symptom was recorded on a grading scale of 0 to 3 (or 0 to 4 for the Shortness of Breath symptom), where higher scores indicated greater severity of symptoms. The total symptom score was calculated as sum of the 10 observed symptom grade values and ranged from 0 to 31, where higher scores indicated more severe symptoms. The overall peak score was defined as the highest scoring symptom diary card observed from the first administration of IMP until quarantine discharge.

ITT-I Population consisted of all randomized participants who received challenge virus and at least 1 dose of IMP and met the criterion for RSV infection.

Individual maximum daily sum of symptom score from initial administration of IMP up to planned discharge from quarantine. The following types of symptoms were recorded: Upper Respiratory Tract (URT): runny nose, stuffy nose, sore throat, sneezing, earache; Lower Respiratory Tract (LRT): cough, shortness of breath; Systemic: headache, malaise, muscle/joint ache/stiffness. Each symptom was recorded on a grading scale of 0 to 3 (or 0 to 4 for the Shortness of Breath symptom), where higher scores indicated greater severity of symptoms. The total symptom score was calculated as sum of the 10 observed symptom grade values and ranged from 0 to 31, where higher scores indicated more severe symptoms. The highest total symptom score recorded on each day, across the three assessments was reported in this outcome measure. The peak daily score was defined as the highest scoring symptom diary card observed on each day from the first administration of IMP until quarantine discharge.

ITT-I Population consisted of all randomized participants who received challenge virus and at least 1 dose of IMP and met the criterion for RSV infection. Here, 'Number Analyzed' signifies participants evaluable for the specified timepoints.

Symptom resolution was defined as a participant scoring 0 for the total symptom score for a 24-hour period (e.g., a minimum of three consecutive symptom diary cards, each with a score of 0) after their peak symptom score. The time from the assessment at the time of the first administration of IMP until symptom resolution was calculated as: Date and time of symptom resolution minus Date and time of assessment at IMP administration. If the peak symptom score occurred on more than one day then the first occurrence was selected. Participants who did not record 24 hours symptom free after their highest total symptom score during the quarantine period were censored at their last assessment.

ITT-I Population consisted of all randomized participants who received challenge virus and at least 1 dose of IMP and met the criterion for RSV infection. Overall Number of Participants Analyzed' signifies participants evaluable for this outcome measure.

Symptom resolution was defined as a participant scoring 0 for the total symptom score for a 24-hour period (e.g., a minimum of three consecutive symptom diary cards, each with a score of 0) after their peak symptom score. The time from the highest total symptom score following administration of IMP until symptom resolution was calculated as: Date and time of symptom resolution minus Date and time of highest total symptom score. If the peak symptom score occurred on more than one day then the first occurrence was selected. Participants who did not record 24 hours symptom free after their highest total symptom score during the quarantine period were censored at their last assessment.

ITT-I Population consisted of all randomized participants who received challenge virus and at least 1 dose of IMP and met the criterion for RSV infection. Overall Number of Participants Analyzed' signifies participants evaluable for this outcome measure.

Time to peak as measured from 10 symptoms within the graded daily symptom scoring system starting from initial administration of IMP to the time of peak daily symptom score. If the peak symptom score occurred on more than one day then the first occurrence was selected. Participants were censored at their last assessment if they did not record any symptoms during the quarantine period.

ITT-I Population consisted of all randomized participants who received challenge virus and at least 1 dose of IMP and met the criterion for RSV infection.

Total weight of nasal mucus was calculated as the sum of mucus weights taken from the assessment at the time of the first administration of IMP (prior to or after dosing, depending on whether dosed in the morning or evening) to morning of Day 12 (Quarantine discharge).

ITT-I Population consisted of all randomized participants who received challenge virus and at least 1 dose of IMP and met the criterion for RSV infection.

Total number of tissues was counted from the assessment at the time of the first dose of IMP (prior to or after dosing, depending on whether dosed in the morning or evening) to morning of Day 12 (Quarantine discharge).

ITT-I Population consisted of all randomized participants who received challenge virus and at least 1 dose of IMP and met the criterion for RSV infection.

An adverse event was defined as any untoward medical occurrence in clinical study participants administered a pharmaceutical product. An AE did not necessarily have a causal relationship with the study intervention. An SAE was defined as any untoward medical occurrence that, at any dose: resulted in death, was life threatening, required inpatient hospitalization or prolongation of existing hospitalization, resulted in persistent disability/incapacity, was a congenital anomaly/birth defect or important medical event.

Safety analysis population was defined as all randomized participants who received challenge virus and at least 1 dose of IMP.

An Adverse Event was defined as any untoward medical occurrence in clinical study participants administered a pharmaceutical product. An AE did not necessarily have a causal relationship with the study intervention. Number of participants with AEs possibly, probably or definitely related to viral challenge agents were reported by preferred terms in this outcome measure.

Safety analysis population was defined as all randomised participants who received challenge virus and at least 1 dose of IMP.

Number of participants with concomitant medications were reported in this outcome measure.

Safety analysis population was defined as all randomized participants who received challenge virus and at least 1 dose of IMP.

Pharmacokinetic (PK) population consisted of all participants from ITT population (all randomized participants who received challenge virus and at least 1 dose of IMP) with at least one post-dose PK result.

PK population consisted of all participants from ITT population (all randomized participants who received challenge virus and at least 1 dose of IMP) with at least one post-dose PK result. Here, 'Number Analyzed' signifies participants evaluable for specified timepoints. t1/2 for dose 1 could not be calculated as at least 3 data points were required in terminal elimination phase within same participant; this criteria could not be fulfilled due to insufficient data above limit of quantification.

PK population consisted of all participants from ITT population (all randomized participants who received challenge virus and at least 1 dose of IMP) with at least one post-dose PK result.

Area under the plasma concentration-time curve from time zero to the end of the dosing interval for RV299 where dosing interval=12 hours.

PK population consisted of all participants from ITT population (all randomized participants who received challenge virus and at least 1 dose of IMP) with at least one post-dose PK result Here, 'Number Analyzed' signifies participants evaluable for the specified timepoints.

PK population consisted of all participants from ITT population (all randomized participants who received challenge virus and at least 1 dose of IMP) with at least one post-dose PK result. Only participants with evaluable results for this PK parameter were reported.

PK population consisted of all participants from ITT population (all randomized participants who received challenge virus and at least 1 dose of IMP) with at least one post-dose PK result. AUC(0-infinity) could not be calculated as atleast 3 data points are required in terminal elimination phase within same participant; this criteria could not be fulfilled due to insufficient data above limit of quantification and did not include a characterization of the terminal elimination.

Participants were administered an oral suspension of placebo twice daily at an interval of approximately 12 hours for 5 consecutive days from Day 2 following confirmation of RSV infection. Participants without a positive result for RSV infection were administered placebo from Day 5.