Placebo capsule matched to molnupiravir taken twice daily by mouth.

RSV A Memphis 37b viral challenge given once by intranasal administration at a dosage of ~4 Log10 plaque forming units (PFUs).

An SAE is any untoward medical occurrence that, at any dose, results in death; is life-threatening; requires hospitalization or prolongs existing hospitalization; results in persistent or significant disability/incapacity; is a congenital anomaly or birth defect; or is another important medical event such as invasive/malignant cancers or substance abuse/dependency. The number of participants who experienced an SAE is reported.

A viral challenge-related AE was defined as any untoward medical occurrence in a clinical study participant, temporally associated with the use of study intervention, that was considered related to the viral challenge (inoculation). The number of participants who experienced AEs related to the viral challenge from viral challenge (Day 0) up to the Day 28 follow-up is reported.

A viral challenge-related SAE was defined as any untoward medical occurrence that, at any dose, resulted in death; was life-threatening; required hospitalization or prolonged existing hospitalization; resulted in persistent or significant disability/incapacity; was a congenital anomaly or birth defect; or was another important medical event, that was considered related to the viral challenge (inoculation). The number of participants who experienced SAEs related to the viral challenge from viral challenge (Day 0) up to the Day 28 follow-up is reported.

Concomitant medications were defined as any prescription medications, over the counter drugs or dietary supplements that a participant happened to be taking while on study, in addition to molnupiravir. The number of participants using concomitant medications from viral challenge (Day 0) up through Day 28 is reported.

VL-AUC between Day 2 and Day 12 after intranasal inoculation (Day 0) was computed for each participant, based on RSV viral load determined by viral quantitative culture (plaque assay) from nasal wash samples collected twice daily (morning and evening). In order to calculate the AUC, the actual time that the assessment was collected was used within the AUC calculation. VL-AUC (on the log10 scale) was analyzed using a linear model with treatment group as a fixed categorical effect. Per protocol, only Panel A (prophylaxis) and Panel C (placebo) were included in the model.

VL-AUC between Day 2 and Day 12 after intranasal inoculation (Day 0) was computed for each participant, based on RSV viral load determined by qRT-PCR from nasal wash samples collected twice daily (morning and evening). In order to calculate the AUC, the actual time that the assessment was collected was used within the AUC calculation. VL-AUC (on the log10 scale) was analyzed using a linear model with treatment group as a fixed categorical effect. Per protocol, only Panel A (prophylaxis) and Panel C (placebo) were included in the model.

PVL was defined as the maximum viral load during a specified time period. PVL as determined by qRT-PCR was measured starting from Day 2 up to planned discharge from quarantine (Day 12 am). Nasal wash samples were collected and tested for RSV viral load by qRT-PCR twice daily from Day 2 through Day 11. A single nasal wash sample for RSV viral load by qRT-PCR was collected on Day 12. PVL by qRT-PCR was analyzed using a linear model with treatment group as a fixed categorical effect. Per protocol, only Panel A (prophylaxis) and Panel C (placebo) were included in the model.

Participants used a symptom diary card to record the daily severity of 10 clinical symptoms on a scale ranging from 0 ("no symptoms") to 3 ("bothersome and interferes with activities"), with the exception of "shortness of breath" symptom which was scored from 0 ("no symptoms") to 4 ("symptoms at rest"). Total symptom scores (TSS) ranged from 0 to 31, with higher scores indicating greater symptom severity. TSS were used to calculate the AUC for each participant based on the available non-missing calculated total symptom scores between Day -1 until Day 12 (quarantine discharge) using the Trapezoidal rule. TSS-AUC was analyzed using a linear model with treatment group as a fixed categorical effect. Per protocol, only Panel A (prophylaxis) and Panel C (placebo) were included in the model. TSS-AUC measured from 10 symptoms within the graded symptom scoring was reported.

Participants used a symptom diary card to record the daily severity of 10 clinical symptoms on a scale ranging from 0 ("absence") to 3 ("bothersome and interferes with activities"), with the exception of "shortness of breath" symptom which was scored from 0 ("no symptoms") to 4 ("symptoms at rest"). TSS ranged from 0 to 31, with higher scores indicating greater symptom severity. TSS were used to calculate the AUC for each participant based on the available non-missing calculated total symptom scores between Day -1 until Day 12 (quarantine discharge) using the Trapezoidal rule. TSS-AUC-CFB was analyzed using a linear model with treatment group as a fixed categorical effect. Per protocol, only Panel A (prophylaxis) and Panel C (placebo) were included in the model. TSS-AUC-CFB was defined as the change from baseline in TSS-AUC from Day -1 up to Day 12. TSS-AUC-CFB measured from 10 symptoms within the graded symptom scoring was reported.

Participants used a symptom diary card to record the daily severity of 10 clinical symptoms on a scale ranging from 0 ("no symptoms") to 3 ("bothersome and interferes with activities"), with the exception of "shortness of breath" symptom which was scored from 0 ("no symptoms") to 4 ("symptoms at rest"). TSS ranged from 0 to 31, with higher scores indicating greater symptom severity. The highest TSS (defined as the sum of all 10 individual composite symptoms) was summarized by treatment group and analyzed using a linear model with treatment group as a fixed categorical effect. Per protocol, only Panel A (prophylaxis) and Panel C (placebo) were included in the model. Peak TSS measured from 10 symptoms within the graded symptom scoring was reported.

Participants used a symptom diary card to record the daily severity of 10 clinical symptoms on a scale ranging from 0 ("no symptoms") to 3 ("bothersome and interferes with activities"), with the exception of "shortness of breath" symptom which was scored from 0 ("no symptoms") to 4 ("symptoms at rest"). TSS ranged from 0 to 31, with higher scores indicating greater symptom severity. The highest total symptom score recorded on each day, across the three assessments, for each participant was summarized descriptively by treatment group and assessment day. Per protocol, only Panel A (prophylaxis) and Panel C (placebo) were included in the analysis. Peak daily sums of symptom score measured from 10 symptoms within the graded symptom scoring were reported for Panels A and C.

A qRT-PCR-confirmed RSV infection was defined as 2 quantifiable (≥ lower limit of quantification [LLOQ]) qRT-PCR measurements (reported on 2 or more independent samples over 2 days), from Day 2 up to Day 12. The number of participants with qRT-PCR-confirmed RSV infection is reported. Per protocol, only Panel A (prophylaxis) and Panel C (placebo) were included in the analysis.

RSV infection based on cell culture measurement was defined as at least one positive (≥ LLOQ) cell culture measurement in nasal swab samples. The percentage of participants with at least one positive (≥ LLOQ) cell culture measurement in nasal swab samples is reported. Per protocol, only Panel A (prophylaxis) and Panel C (placebo) were included in the analysis.

Symptomatic RSV infection was defined as 2 quantifiable (≥LLOQ) qRT-PCR measurements reported on 2 or more days and either one or more clinical symptoms of any grade from two different categories in the symptom scoring system (upper respiratory, lower respiratory, systemic) or one grade 2 symptom from any category. The percentage of participants with qRT-PCR-confirmed symptomatic RSV infection is reported. Per protocol, only Panel A (prophylaxis) and Panel C (placebo) were included in the analysis.

Moderately severe symptomatic RSV infection was defined as 2 quantifiable (≥LLOQ) qRT-PCR measurements reported on 2 or more consecutive days and any symptom scores of grade ≥2 at a single time point. The percentage of participants with qRT-PCR-confirmed moderately severe symptomatic RSV infection is reported. Per protocol, only Panel A (prophylaxis) and Panel C (placebo) were included in the analysis.

Culture-confirmed symptomatic RSV infection was defined by 1 quantifiable (≥LLOQ) cell culture measurement from Day 2 up to Day 12, and either one or more clinical symptoms of any grade from two different categories in the symptom scoring system (upper respiratory, lower respiratory, systemic) or one grade 2 symptom from any category. The percentage of participants with culture confirmed symptomatic RSV infection is reported. Per protocol, only Panel A (prophylaxis) and Panel C (placebo) were included in the analysis.

PVL was defined as the maximum viral load during a specified time period. PVL as determined by viral quantitative culture was measured starting from Day 2 up to planned discharge from quarantine (Day 12 am). PVL (on the log10 scale) of RSV A Memphis 37b determined by viral quantitative culture (plaque assay) between Day 2 and Day 12 am after intranasal inoculation (Day 0) was analyzed using a linear model with treatment group as a fixed categorical effect. Per protocol, only Panel B (treatment) and Panel C (placebo) are included in the model. For both panels, only the participants with RSV infection were included in the analysis.

The time to negative test was defined as length of time in days between the date and time of the first MK-4482 administration to the date and time of first confirmed negative test after peak viral culture measurement. A negative test is a result below the low limit of quantification (LLOQ) by viral quantitative culture (plaque assay). The Kaplan-Meier estimate median in days is reported. Per protocol, only Panel B (treatment) and Panel C (placebo) are included in the model. For both panels, only the participants with RSV infection were included in the analysis.

VL-AUC between Day 2 and Day 12 after intranasal inoculation (Day 0) was computed for each participant, based on RSV viral load determined by qRT-PCR from nasal wash samples collected twice daily (morning and evening). In order to calculate the AUC, the actual time that the assessment was collected was used within the AUC calculation. VL-AUC (on the log10 scale) was analyzed using a linear model with treatment group as a fixed categorical effect. Per protocol, only Panel B (treatment) and Panel C (placebo) are included in the model. For both panels, only the participants with RSV infection were included in the analysis.

PVL was defined as the maximum viral load during a specified time period. PVL as determined by qRT-PCR was measured starting from Day 2 up to planned discharge from quarantine (Day 12 am). Nasal wash samples were collected and tested for RSV viral load by qRT-PCR twice daily from Day 2 through Day 11. A single nasal wash sample for RSV viral load by qRT-PCR was collected on Day 12. PVL by qRT-PCR were analyzed using a linear model with treatment group as a fixed categorical effect. Per protocol, only Panel B (treatment) and Panel C (placebo) are included in the model. For both panels, only the participants with RSV infection were included in the analysis.

The time (days) to confirmed negative test by qRT-PCR was defined as the length of time between the date and time of the first investigational medicinal product (IMP) administration to the date and time of first confirmed undetectable (\

Participants used a symptom diary card to record the daily severity of 10 clinical symptoms on a scale ranging from 0 ("no symptoms") to 3 ("bothersome and interferes with activities"), with the exception of "shortness of breath" symptom which was scored from 0 ("no symptoms") to 4 ("symptoms at rest"). Total symptom scores (TSS) ranged from 0 to 31, with higher scores indicating greater symptom severity. TSS were used to calculate the AUC for each participant based on the available non-missing calculated total symptom scores between Day -1 until Day 12 (quarantine discharge) using the Trapezoidal rule. TSS-AUC was analyzed using a linear model with treatment group as a fixed categorical effect. Per protocol, only Panel B and Panel C are included in the model, and only participants with RSV infection were included in the analysis. TSS-AUC measured from 10 symptoms within the graded symptom scoring was reported.

Participants used a symptom diary card to record the daily severity of 10 clinical symptoms on a scale ranging from 0 ("absence") to 3 ("bothersome and interferes with activities"), with the exception of "shortness of breath" symptom which was scored from 0 ("no symptoms") to 4 ("symptoms at rest"). TSS ranged from 0 to 31, with higher scores indicating greater symptom severity. TSS were used to calculate the AUC for each participant based on the available non-missing calculated total symptom scores between Day -1 until Day 12 (quarantine discharge) using the Trapezoidal rule. TSS-AUC-CFB was analyzed using a linear model with treatment group as a fixed categorical effect. Per protocol, only Panel B and Panel C are included in the model, and only the participants with RSV infection were included in the analysis. TSS-AUC-CFB was defined as the change from baseline in TSS-AUC from Day -1 up to Day 12. TSS-AUC-CFB measured from 10 symptoms within the graded symptom scoring was reported.

Participants used a symptom diary card to record the daily severity of 10 clinical symptoms on a scale ranging from 0 ("no symptoms") to 3 ("bothersome and interferes with activities"), with the exception of "shortness of breath" symptom which was scored from 0 ("no symptoms") to 4 ("symptoms at rest"). TSS ranged from 0 to 31, with higher scores indicating greater symptom severity. The highest total symptom score (defined as the sum of all 10 individual composite symptoms) was summarized by treatment group and analyzed using a linear model with treatment group as a fixed categorical effect. Peak TSS measured from 10 symptoms within the graded symptom scoring was reported for Panels B and C. Per protocol, only Panel B (treatment) and Panel C (placebo) are included in the model. For both panels, only the participants with RSV infection were included in the analysis.

Participants used a symptom diary card to record the daily severity of 10 clinical symptoms on a scale ranging from 0 ("no symptoms") to 3 ("bothersome and interferes with activities"), with the exception of "shortness of breath" symptom which was scored from 0 ("no symptoms") to 4 ("symptoms at rest"). TSS ranged from 0 to 31, with higher scores indicating greater symptom severity. The highest total symptom score recorded on each day, across the three assessments, for each participant was summarized descriptively by treatment group and assessment day. Peak daily sums of symptom score measured from 10 symptoms within the graded symptom scoring were reported for Panels B and C. Per protocol, only Panel B (treatment) and Panel C (placebo) are included in the model. For both panels, only the participants with RSV infection were included in the analysis.

Participants used a symptom diary card to record the daily severity of 10 clinical symptoms on a scale ranging from 0 ("no symptoms") to 3 ("bothersome and interferes with activities"), with the exception of "shortness of breath" symptom which was scored from 0 ("no symptoms") to 4 ("symptoms at rest"). TSS ranged from 0 to 31, with higher scores indicating greater symptom severity. 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 in days to symptom resolution by treatment group, as measured from 10 symptoms within the graded daily symptom scoring system, was reported. Per protocol, only Panel B (treatment) and Panel C (placebo) are included in the model. For both panels, only the participants with RSV infection were included in the analysis.

NHC is the pharmacologically active moiety of molnupiravir and therefore its primary pharmacokinetic measure. Cmax was defined as the peak concentration of NHC over the dosing interval. Plasma samples were collected at multiple time points pre-and post-administration and used to determine Cmax. Cmax of NHC was reported for participants receiving molnupiravir in Panels A and B.

NHC is the pharmacologically active moiety of molnupiravir and therefore its primary pharmacokinetic measure. Tmax was defined as the time to peak concentration. Plasma samples were collected at multiple time points pre-and post-administration and used to determine Tmax. Tmax of NHC was reported for participants receiving molnupiravir in Panels A and B.

NHC is the pharmacologically active moiety of molnupiravir and therefore its primary pharmacokinetic measure. Plasma samples were collected at multiple time points pre-and post-administration and used to determine the area under the plasma concentration curve from time 0 to 12 hours (AUC0-12). AUC0-12 was reported for participants receiving molnupiravir in Panels A and B.

NHC is the pharmacologically active moiety of molnupiravir and therefore its primary pharmacokinetic measure. The trough concentration (Ctrough) was defined as the lowest concentration before the next dose. Plasma samples were collected at multiple time points pre-and post-administration and used to determine Cmax. Ctrough of NHC in plasma was reported for participants receiving molnupiravir in Panels A and B.

Participants received placebo beginning on Day -1, were inoculated with RSV-A Memphis 37b on Day 0, and continued receiving placebo until the morning of Day 10.

Total of all reporting groups

Participants received placebo beginning on Day -1, were inoculated with RSV-A Memphis 37b on Day 0, and continued receiving placebo until the morning of Day 10.

VL-AUC between Day 2 and Day 12 after intranasal inoculation (Day 0) was computed for each participant, based on RSV viral load determined by viral quantitative culture (plaque assay) from nasal wash samples collected twice daily (morning and evening). In order to calculate the AUC, the actual time that the assessment was collected was used within the AUC calculation. VL-AUC (on the log10 scale) was analyzed using a linear model with treatment group as a fixed categorical effect. Per protocol, only Panel B (treatment) and Panel C (placebo) were included in the model. For both panels, only the participants with RSV infection were included.

All randomized participants in Panel B or Panel C who received 1 dose of the correct clinical material corresponding to the treatment group the participants were randomized into, who received the viral inoculation, were determined to be RSV infected, and had available VL-AUC viral quantitative culture data. Per protocol, Panel A was not included in this analysis.

An AE is any untoward medical occurrence in a clinical study participant, temporally associated with the use of study intervention, whether or not considered related to the study intervention. The number of participants who experienced an AE is reported.

All participants who received at least one dose of treatment.

An SAE is any untoward medical occurrence that, at any dose, results in death; is life-threatening; requires hospitalization or prolongs existing hospitalization; results in persistent or significant disability/incapacity; is a congenital anomaly or birth defect; or is another important medical event such as invasive/malignant cancers or substance abuse/dependency. The number of participants who experienced an SAE is reported.

All participants who received at least one dose of treatment.

A viral challenge-related AE was defined as any untoward medical occurrence in a clinical study participant, temporally associated with the use of study intervention, that was considered related to the viral challenge (inoculation). The number of participants who experienced AEs related to the viral challenge from viral challenge (Day 0) up to the Day 28 follow-up is reported.

All participants who received at least one dose of treatment.

A viral challenge-related SAE was defined as any untoward medical occurrence that, at any dose, resulted in death; was life-threatening; required hospitalization or prolonged existing hospitalization; resulted in persistent or significant disability/incapacity; was a congenital anomaly or birth defect; or was another important medical event, that was considered related to the viral challenge (inoculation). The number of participants who experienced SAEs related to the viral challenge from viral challenge (Day 0) up to the Day 28 follow-up is reported.

All participants who received at least one dose of treatment.

Concomitant medications were defined as any prescription medications, over the counter drugs or dietary supplements that a participant happened to be taking while on study, in addition to molnupiravir. The number of participants using concomitant medications from viral challenge (Day 0) up through Day 28 is reported.

All participants who received at least one dose of treatment.

VL-AUC between Day 2 and Day 12 after intranasal inoculation (Day 0) was computed for each participant, based on RSV viral load determined by viral quantitative culture (plaque assay) from nasal wash samples collected twice daily (morning and evening). In order to calculate the AUC, the actual time that the assessment was collected was used within the AUC calculation. VL-AUC (on the log10 scale) was analyzed using a linear model with treatment group as a fixed categorical effect. Per protocol, only Panel A (prophylaxis) and Panel C (placebo) were included in the model.

All randomized participants in Panel A or Panel C who received 1 dose of the correct clinical material corresponding to the treatment group the participants were randomized into, who received the viral inoculation, and had available VL-AUC viral quantitative culture data. Per protocol, Panel B was not included in the analysis.

VL-AUC between Day 2 and Day 12 after intranasal inoculation (Day 0) was computed for each participant, based on RSV viral load determined by qRT-PCR from nasal wash samples collected twice daily (morning and evening). In order to calculate the AUC, the actual time that the assessment was collected was used within the AUC calculation. VL-AUC (on the log10 scale) was analyzed using a linear model with treatment group as a fixed categorical effect. Per protocol, only Panel A (prophylaxis) and Panel C (placebo) were included in the model.

All randomized participants in Panel A or Panel C who received 1 dose of the correct clinical material corresponding to the treatment group the participants were randomized into and who received the viral inoculation. Per protocol, Panel B was not included in the analysis.

PVL was defined as the maximum viral load during a specified time period. PVL as determined by qRT-PCR was measured starting from Day 2 up to planned discharge from quarantine (Day 12 am). Nasal wash samples were collected and tested for RSV viral load by qRT-PCR twice daily from Day 2 through Day 11. A single nasal wash sample for RSV viral load by qRT-PCR was collected on Day 12. PVL by qRT-PCR was analyzed using a linear model with treatment group as a fixed categorical effect. Per protocol, only Panel A (prophylaxis) and Panel C (placebo) were included in the model.

All randomized participants in Panel A or Panel C who received 1 dose of the correct clinical material corresponding to the treatment group the participants were randomized into, who received the viral inoculation, and had available PVL qRT-PCR data. Per protocol, Panel B was not included in this analysis.

Participants used a symptom diary card to record the daily severity of 10 clinical symptoms on a scale ranging from 0 ("no symptoms") to 3 ("bothersome and interferes with activities"), with the exception of "shortness of breath" symptom which was scored from 0 ("no symptoms") to 4 ("symptoms at rest"). Total symptom scores (TSS) ranged from 0 to 31, with higher scores indicating greater symptom severity. TSS were used to calculate the AUC for each participant based on the available non-missing calculated total symptom scores between Day -1 until Day 12 (quarantine discharge) using the Trapezoidal rule. TSS-AUC was analyzed using a linear model with treatment group as a fixed categorical effect. Per protocol, only Panel A (prophylaxis) and Panel C (placebo) were included in the model. TSS-AUC measured from 10 symptoms within the graded symptom scoring was reported.

All randomized participants in Panel A or Panel C who received 1 dose of the correct clinical material corresponding to the treatment group the participants were randomized into, who received the viral inoculation, and had available TSS data. Per protocol, Panel B was not included in this analysis.

Participants used a symptom diary card to record the daily severity of 10 clinical symptoms on a scale ranging from 0 ("absence") to 3 ("bothersome and interferes with activities"), with the exception of "shortness of breath" symptom which was scored from 0 ("no symptoms") to 4 ("symptoms at rest"). TSS ranged from 0 to 31, with higher scores indicating greater symptom severity. TSS were used to calculate the AUC for each participant based on the available non-missing calculated total symptom scores between Day -1 until Day 12 (quarantine discharge) using the Trapezoidal rule. TSS-AUC-CFB was analyzed using a linear model with treatment group as a fixed categorical effect. Per protocol, only Panel A (prophylaxis) and Panel C (placebo) were included in the model. TSS-AUC-CFB was defined as the change from baseline in TSS-AUC from Day -1 up to Day 12. TSS-AUC-CFB measured from 10 symptoms within the graded symptom scoring was reported.

All randomized participants in Panel A or Panel C who received 1 dose of the correct clinical material corresponding to the treatment group the participants were randomized into, who received the viral inoculation, and had available TSS data. Per protocol, Panel B was not included in this analysis.

Participants used a symptom diary card to record the daily severity of 10 clinical symptoms on a scale ranging from 0 ("no symptoms") to 3 ("bothersome and interferes with activities"), with the exception of "shortness of breath" symptom which was scored from 0 ("no symptoms") to 4 ("symptoms at rest"). TSS ranged from 0 to 31, with higher scores indicating greater symptom severity. The highest TSS (defined as the sum of all 10 individual composite symptoms) was summarized by treatment group and analyzed using a linear model with treatment group as a fixed categorical effect. Per protocol, only Panel A (prophylaxis) and Panel C (placebo) were included in the model. Peak TSS measured from 10 symptoms within the graded symptom scoring was reported.

All randomized participants in Panel A or Panel C who received 1 dose of the correct clinical material corresponding to the treatment group the participants were randomized into, who received the viral inoculation, and had available TSS data. Per protocol, Panel B was not included in this analysis.

Participants used a symptom diary card to record the daily severity of 10 clinical symptoms on a scale ranging from 0 ("no symptoms") to 3 ("bothersome and interferes with activities"), with the exception of "shortness of breath" symptom which was scored from 0 ("no symptoms") to 4 ("symptoms at rest"). TSS ranged from 0 to 31, with higher scores indicating greater symptom severity. The highest total symptom score recorded on each day, across the three assessments, for each participant was summarized descriptively by treatment group and assessment day. Per protocol, only Panel A (prophylaxis) and Panel C (placebo) were included in the analysis. Peak daily sums of symptom score measured from 10 symptoms within the graded symptom scoring were reported for Panels A and C.

All randomized participants in Panel A or Panel C who received 1 dose of the correct clinical material corresponding to the treatment group the participants were randomized into, who received the viral inoculation, and had available TSS data. Per protocol, Panel B was not included in this analysis.

A qRT-PCR-confirmed RSV infection was defined as 2 quantifiable (≥ lower limit of quantification [LLOQ]) qRT-PCR measurements (reported on 2 or more independent samples over 2 days), from Day 2 up to Day 12. The number of participants with qRT-PCR-confirmed RSV infection is reported. Per protocol, only Panel A (prophylaxis) and Panel C (placebo) were included in the analysis.

All randomized participants in Panel A or Panel C who received 1 dose of the correct clinical material corresponding to the treatment group the participants were randomized into, who received the viral inoculation, and had available RSV infection qRT-PCR data. Per protocol, Panel B was not included in this analysis.

RSV infection based on cell culture measurement was defined as at least one positive (≥ LLOQ) cell culture measurement in nasal swab samples. The percentage of participants with at least one positive (≥ LLOQ) cell culture measurement in nasal swab samples is reported. Per protocol, only Panel A (prophylaxis) and Panel C (placebo) were included in the analysis.

All randomized participants in Panel A or Panel C who received 1 dose of the correct clinical material corresponding to the treatment group the participants were randomized into, who received the viral inoculation, and had at least 1 available positive RSV cell culture measurement data. Per protocol, Panel B was not included in this analysis.

Symptomatic RSV infection was defined as 2 quantifiable (≥LLOQ) qRT-PCR measurements reported on 2 or more days and either one or more clinical symptoms of any grade from two different categories in the symptom scoring system (upper respiratory, lower respiratory, systemic) or one grade 2 symptom from any category. The percentage of participants with qRT-PCR-confirmed symptomatic RSV infection is reported. Per protocol, only Panel A (prophylaxis) and Panel C (placebo) were included in the analysis.

All randomized participants in Panel A or Panel C who received 1 dose of the correct clinical material corresponding to the treatment group the participants were randomized into, who received the viral inoculation, and had available RSV symptomatic infection data. Per protocol, Panel B was not included in this analysis.

Moderately severe symptomatic RSV infection was defined as 2 quantifiable (≥LLOQ) qRT-PCR measurements reported on 2 or more consecutive days and any symptom scores of grade ≥2 at a single time point. The percentage of participants with qRT-PCR-confirmed moderately severe symptomatic RSV infection is reported. Per protocol, only Panel A (prophylaxis) and Panel C (placebo) were included in the analysis.

All randomized participants in Panel A or Panel C who received 1 dose of the correct clinical material corresponding to the treatment group the participants were randomized into, who received the viral inoculation, and had available RSV symptomatic infection data. Per protocol, Panel B was not included in this analysis.

Culture-confirmed symptomatic RSV infection was defined by 1 quantifiable (≥LLOQ) cell culture measurement from Day 2 up to Day 12, and either one or more clinical symptoms of any grade from two different categories in the symptom scoring system (upper respiratory, lower respiratory, systemic) or one grade 2 symptom from any category. The percentage of participants with culture confirmed symptomatic RSV infection is reported. Per protocol, only Panel A (prophylaxis) and Panel C (placebo) were included in the analysis.

All randomized participants in Panel A or Panel C who received 1 dose of the correct clinical material corresponding to the treatment group the participants were randomized into, who received the viral inoculation, and had available RSV symptomatic infection data. Per protocol, Panel B was not included in this analysis.

PVL was defined as the maximum viral load during a specified time period. PVL as determined by viral quantitative culture was measured starting from Day 2 up to planned discharge from quarantine (Day 12 am). PVL (on the log10 scale) of RSV A Memphis 37b determined by viral quantitative culture (plaque assay) between Day 2 and Day 12 am after intranasal inoculation (Day 0) was analyzed using a linear model with treatment group as a fixed categorical effect. Per protocol, only Panel B (treatment) and Panel C (placebo) are included in the model. For both panels, only the participants with RSV infection were included in the analysis.

All randomized participants in Panel B or Panel C who received 1 dose of the correct clinical material corresponding to the treatment group the participants were randomized into, who received the viral inoculation, were determined to be RSV infected, and had available PVL viral quantitative culture data. Per protocol, Panel A was not included in this analysis.

The time to negative test was defined as length of time in days between the date and time of the first MK-4482 administration to the date and time of first confirmed negative test after peak viral culture measurement. A negative test is a result below the low limit of quantification (LLOQ) by viral quantitative culture (plaque assay). The Kaplan-Meier estimate median in days is reported. Per protocol, only Panel B (treatment) and Panel C (placebo) are included in the model. For both panels, only the participants with RSV infection were included in the analysis.

All randomized participants in Panel B or Panel C who received 1 dose of the correct clinical material corresponding to the treatment group the participants were randomized into, who received the viral inoculation, were determined to be RSV infected, and had available negative test by viral quantitative culture data. Per protocol, Panel A was not included in this analysis.

VL-AUC between Day 2 and Day 12 after intranasal inoculation (Day 0) was computed for each participant, based on RSV viral load determined by qRT-PCR from nasal wash samples collected twice daily (morning and evening). In order to calculate the AUC, the actual time that the assessment was collected was used within the AUC calculation. VL-AUC (on the log10 scale) was analyzed using a linear model with treatment group as a fixed categorical effect. Per protocol, only Panel B (treatment) and Panel C (placebo) are included in the model. For both panels, only the participants with RSV infection were included in the analysis.

All randomized participants in Panel B or Panel C who received 1 dose of the correct clinical material corresponding to the treatment group the participants were randomized into, who received the viral inoculation, were determined to be RSV infected, and had available VL-AUC qRT-PCR data. Per protocol, Panel A was not included in this analysis.

PVL was defined as the maximum viral load during a specified time period. PVL as determined by qRT-PCR was measured starting from Day 2 up to planned discharge from quarantine (Day 12 am). Nasal wash samples were collected and tested for RSV viral load by qRT-PCR twice daily from Day 2 through Day 11. A single nasal wash sample for RSV viral load by qRT-PCR was collected on Day 12. PVL by qRT-PCR were analyzed using a linear model with treatment group as a fixed categorical effect. Per protocol, only Panel B (treatment) and Panel C (placebo) are included in the model. For both panels, only the participants with RSV infection were included in the analysis.

All randomized participants in Panel B or Panel C who received 1 dose of the correct clinical material corresponding to the treatment group the participants were randomized into, who received the viral inoculation, were determined to be RSV infected, and had available PVL qRT-PCR data. Per protocol, Panel A was not included in this analysis.

The time (days) to confirmed negative test by qRT-PCR was defined as the length of time between the date and time of the first investigational medicinal product (IMP) administration to the date and time of first confirmed undetectable (\

All randomized participants in Panel B or Panel C who received 1 dose of the correct clinical material corresponding to the treatment group the participants were randomized into, who received the viral inoculation, were determined to be RSV infected, and had available negative test qRT-PCR data. Per protocol, Panel A was not included in this analysis.

Participants used a symptom diary card to record the daily severity of 10 clinical symptoms on a scale ranging from 0 ("no symptoms") to 3 ("bothersome and interferes with activities"), with the exception of "shortness of breath" symptom which was scored from 0 ("no symptoms") to 4 ("symptoms at rest"). Total symptom scores (TSS) ranged from 0 to 31, with higher scores indicating greater symptom severity. TSS were used to calculate the AUC for each participant based on the available non-missing calculated total symptom scores between Day -1 until Day 12 (quarantine discharge) using the Trapezoidal rule. TSS-AUC was analyzed using a linear model with treatment group as a fixed categorical effect. Per protocol, only Panel B and Panel C are included in the model, and only participants with RSV infection were included in the analysis. TSS-AUC measured from 10 symptoms within the graded symptom scoring was reported.

All randomized participants in Panel B or Panel C who received 1 dose of the correct clinical material corresponding to the treatment group the participants were randomized into, who received the viral inoculation, were determined to be RSV infected, and had available TSS data. Per protocol, Panel A was not included in this analysis.

Participants used a symptom diary card to record the daily severity of 10 clinical symptoms on a scale ranging from 0 ("absence") to 3 ("bothersome and interferes with activities"), with the exception of "shortness of breath" symptom which was scored from 0 ("no symptoms") to 4 ("symptoms at rest"). TSS ranged from 0 to 31, with higher scores indicating greater symptom severity. TSS were used to calculate the AUC for each participant based on the available non-missing calculated total symptom scores between Day -1 until Day 12 (quarantine discharge) using the Trapezoidal rule. TSS-AUC-CFB was analyzed using a linear model with treatment group as a fixed categorical effect. Per protocol, only Panel B and Panel C are included in the model, and only the participants with RSV infection were included in the analysis. TSS-AUC-CFB was defined as the change from baseline in TSS-AUC from Day -1 up to Day 12. TSS-AUC-CFB measured from 10 symptoms within the graded symptom scoring was reported.

All randomized participants in Panel B or Panel C who received 1 dose of the correct clinical material corresponding to the treatment group the participants were randomized into, who received the viral inoculation, were determined to be RSV infected, and had available TSS data. Per protocol, Panel A was not included in this analysis.

Participants used a symptom diary card to record the daily severity of 10 clinical symptoms on a scale ranging from 0 ("no symptoms") to 3 ("bothersome and interferes with activities"), with the exception of "shortness of breath" symptom which was scored from 0 ("no symptoms") to 4 ("symptoms at rest"). TSS ranged from 0 to 31, with higher scores indicating greater symptom severity. The highest total symptom score (defined as the sum of all 10 individual composite symptoms) was summarized by treatment group and analyzed using a linear model with treatment group as a fixed categorical effect. Peak TSS measured from 10 symptoms within the graded symptom scoring was reported for Panels B and C. Per protocol, only Panel B (treatment) and Panel C (placebo) are included in the model. For both panels, only the participants with RSV infection were included in the analysis.

All randomized participants in Panel B or Panel C who received 1 dose of the correct clinical material corresponding to the treatment group the participants were randomized into, who received the viral inoculation, were determined to be RSV infected, and had available TSS data. Per protocol, Panel A was not included in this analysis.

Participants used a symptom diary card to record the daily severity of 10 clinical symptoms on a scale ranging from 0 ("no symptoms") to 3 ("bothersome and interferes with activities"), with the exception of "shortness of breath" symptom which was scored from 0 ("no symptoms") to 4 ("symptoms at rest"). TSS ranged from 0 to 31, with higher scores indicating greater symptom severity. The highest total symptom score recorded on each day, across the three assessments, for each participant was summarized descriptively by treatment group and assessment day. Peak daily sums of symptom score measured from 10 symptoms within the graded symptom scoring were reported for Panels B and C. Per protocol, only Panel B (treatment) and Panel C (placebo) are included in the model. For both panels, only the participants with RSV infection were included in the analysis.

All randomized participants in Panel B or Panel C who received 1 dose of the correct clinical material corresponding to the treatment group the participants were randomized into, who received the viral inoculation, were determined to be RSV infected, and had available TSS data. Per protocol, Panel A was not included in this analysis.

Participants used a symptom diary card to record the daily severity of 10 clinical symptoms on a scale ranging from 0 ("no symptoms") to 3 ("bothersome and interferes with activities"), with the exception of "shortness of breath" symptom which was scored from 0 ("no symptoms") to 4 ("symptoms at rest"). TSS ranged from 0 to 31, with higher scores indicating greater symptom severity. 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 in days to symptom resolution by treatment group, as measured from 10 symptoms within the graded daily symptom scoring system, was reported. Per protocol, only Panel B (treatment) and Panel C (placebo) are included in the model. For both panels, only the participants with RSV infection were included in the analysis.

All randomized participants in Panel B or Panel C who received 1 dose of the correct clinical material corresponding to the treatment group the participants were randomized into, who received the viral inoculation, were determined to be RSV infected, and had available symptom resolution data. Per protocol, Panel A was not included in this analysis.

NHC is the pharmacologically active moiety of molnupiravir and therefore its primary pharmacokinetic measure. Cmax was defined as the peak concentration of NHC over the dosing interval. Plasma samples were collected at multiple time points pre-and post-administration and used to determine Cmax. Cmax of NHC was reported for participants receiving molnupiravir in Panels A and B.

All randomized participants in Panels A and B who received at least one dose of molnupiravir and received viral inoculation, with available measurements and without important protocol deviations. Per protocol, Panel C participants receiving placebo were not included in the analysis.

NHC is the pharmacologically active moiety of molnupiravir and therefore its primary pharmacokinetic measure. Tmax was defined as the time to peak concentration. Plasma samples were collected at multiple time points pre-and post-administration and used to determine Tmax. Tmax of NHC was reported for participants receiving molnupiravir in Panels A and B.

All randomized participants in Panels A and B who received at least one dose of molnupiravir and received viral inoculation, with available measurements and without important protocol deviations. Per protocol, Panel C participants receiving placebo were not included in the analysis.

NHC is the pharmacologically active moiety of molnupiravir and therefore its primary pharmacokinetic measure. Plasma samples were collected at multiple time points pre-and post-administration and used to determine the area under the plasma concentration curve from time 0 to 12 hours (AUC0-12). AUC0-12 was reported for participants receiving molnupiravir in Panels A and B.

All randomized participants in Panels A and B who received at least one dose of molnupiravir and received viral inoculation, with available measurements and without important protocol deviations. Per protocol, Panel C participants receiving placebo were not included in the analysis.

NHC is the pharmacologically active moiety of molnupiravir and therefore its primary pharmacokinetic measure. The trough concentration (Ctrough) was defined as the lowest concentration before the next dose. Plasma samples were collected at multiple time points pre-and post-administration and used to determine Cmax. Ctrough of NHC in plasma was reported for participants receiving molnupiravir in Panels A and B.

All randomized participants in Panels A and B who received at least one dose of molnupiravir and received viral inoculation, with available measurements and without important protocol deviations. Per protocol, Panel C participants receiving placebo were not included in the analysis.

Participants received placebo on Day -1, were inoculated with RSV-A Memphis 37b on Day 0, and continued to receive placebo until testing positive for RSV. Participants then received 800 mg of molnupiravir every 12 hours for 5 days.

Participants received placebo beginning on Day -1, were inoculated with RSV-A Memphis 37b on Day 0, and continued receiving placebo until the morning of Day 10.