RiiQ symptom scale is 13-item questionnaire (6 symptoms related to upper & lower respiratory tract & 7 systemic symptoms).Targeted RSV symptoms are 6 respiratory symptoms: nasal congestion, sore throat, cough, expectoration, shortness of breath & wheezing.Each symptom is rated on scale of None, Mild, Moderate & Severe.Alleviation of targeted RSV symptoms was defined as for 2 consecutive assessments: non-preexisting symptoms scored was None or Mild; pre-existing symptoms that were present but not worse at baseline scored same or below;& pre-existing symptoms that were worse at baseline improved at least one scale grade level. Time to alleviation of targeted RSV symptoms by Day 15 for participants with symptom alleviation was calculated as symptom alleviation date/time minus first dose date/time.For participants who completed or discontinued study by Day 15 without symptom alleviation (censored),time was calculated as last date/time on which RiiQ was assessed minus first dose date/time.

The Full Analysis Positive Set (FAPS) included all randomized participants who received at least 1 dose of study drug and were RSV positive at baseline by a central laboratory test. Kaplan-Meier (KM) estimates were used in analysis.

An adverse event (AE) is any untoward medical occurrence in a clinical study participant administered a study drug that does not necessarily have a causal relationship with the treatment. An AE can therefore be any unfavorable and/or unintended sign, symptom, or disease temporally associated with the use of a study drug, whether or not the AE is considered related to the study drug. TEAEs were defined as any AE that began on or after the date of first dose of study drug up to the date of last dose of study drug plus 30 days and that led to study drug discontinuation. Percentages are rounded off.

The Safety Analysis Set included all randomized participants who took at least 1 dose of study drug.

Treatment-emergent laboratory abnormalities are defined as values that increase at least 1 toxicity grade from baseline at any postbaseline time point up to the date of the last dose of study drug plus 30 days. The Division of AIDS (DAIDS) Toxicity Grading Scale, Version 2.1 was used to assign toxicity grades (0 to 4) to laboratory results for analysis. Grade 0 included all values that did not meet the criteria for an abnormality of at least Grade 1. Grade 1: mild, Grade 2: moderate, Grade 3: severe, and Grade 4: potentially life-threatening. Percentage are rounded off.

Participants in Safety Analysis Set with at least 1 postbaseline laboratory value available were analyzed.

A serious adverse event (SAEs) is defined as an event that, at any dose, results in death, a life-threatening situation, inpatient hospitalization or prolongation of existing hospitalization, persistent or significant disability/incapacity, a congenital anomaly/birth defect, or a medically important event or reaction. Percentage was rounded off.

Participants in the Safety Analysis Set were analyzed.

TEAEs were defined as any AE that began on or after the date of first dose of study drug up to the date of last dose of study drug plus 30 days and that led to study drug discontinuation. Percentages are rounded off.

Participants in the Safety Analysis Set were analyzed.

RiiQ and targeted RSV symptoms are defined in Outcome Measure #1. Each symptom is rated on scale of None, Mild, Moderate, & Severe. Sustained alleviation of targeted RSV symptoms was defined similarly to alleviation of targeted RSV symptoms but for 3 consecutive assessments. Time to sustained alleviation of targeted RSV symptoms by Day 15 for participants with sustained symptom alleviation was calculated as symptom alleviation date/time minus first dose date/time. For participants who completed or discontinued study by Day 15 without sustained symptom alleviation (censored), time was calculated as last date/time on which RiiQ was assessed minus first dose date/time.

Participants in the Full Analysis Positive Set were analyzed. KM estimates were used for analysis.

RiiQ is defined in Outcome Measure #1. Lower Respiratory Tract (LRT) symptoms included cough, expectoration, shortness of breath, and wheezing. Based on RiiQ, RSV-related LRTI was defined as >=2 of the following symptoms, 1 of which must be reported as at least 'moderate' severity: new or increased cough, new or increased wheezing, new or increased shortness of breath, new or increased expectoration and participant has not met alleviation endpoints. The time to RSV-related LRTI by Day 29 for participants with RSV-related LRTI, was calculated as date/time of meeting LRTI definition minus first dose date/time. For participants who completed Day 29 of the study or discontinued from the study before Day 29 without RSV-related LRTI (censored), time was calculated as last date/time on which RiiQ was assessed minus the first dose date/time.

Participants in the Full Analysis Positive Set were analyzed. KM estimates were used in analysis.

RSV-related hospitalization is defined as ≥ 24 hours of acute care for a reason related to RSV, in a hospital or similar acute care facility, including emergency rooms or temporary facilities instituted to address medical needs of those with RSV. RSV relatedness was determined by investigator. KM estimates were used in analysis.

Participants in the Full Analysis Positive Set were analyzed.

Medically attended visits (MAV) are defined as any interactions with health care professionals other than study staff or designees, including hospitalization; in-person emergency, urgent, or primary care visits; or any other in-person visit attended by the participant and a health care professional. RSV relatedness was determined by the investigator. KM estimates were used in analysis.

Participants in the Full Analysis Positive Set were analyzed.

The RSV viral load results were obtained from UTM (universal transport medium) nasal swab samples collected at Baseline.

The UTM Nasal Swab Virology Analysis Set included all randomized participants who took at least 1 dose of study drug and who had a baseline RSV viral load in UTM nasal swab samples greater than or equal to the lower limit of quantitation.

The RSV viral load results were obtained from UTM nasal swab samples collected at Baseline and Day 3.

Participants in the UTM Nasal Swab Virology Analysis Set with available data were analyzed.

The RSV viral load results were obtained from UTM nasal swab samples collected at Baseline and Day 5.

Participants in the UTM Nasal Swab Virology Analysis Set with available data were analyzed.

The RSV viral load results were obtained from UTM nasal swab samples collected at Baseline and Day 7.

Participants in UTM Nasal Swab Virology Analysis Set with available data were analyzed.

The RSV viral load results were obtained from UTM nasal swab samples collected at Baseline and Day 10.

Participants in UTM Nasal Swab Virology Analysis Set with available data were analyzed.

The RSV viral load results were obtained from UTM nasal swab samples collected at Baseline and Day 15.

Participants in UTM Nasal Swab Virology Analysis Set with available data were analyzed.

AUCtau is defined as area under the plasma concentration-time curve during a dosing interval.

The Intensive Venous Blood PK Analysis Set included all randomized participants in the optional intensive PK substudy who received ≥ 1 dose of study drug and had ≥ 1 nonmissing intensive PK concentration value from venous blood reported by the PK laboratory for GS-441524. Participants with available data were analyzed.

Ctrough is defined as the concentration at the end of the dosing interval.

Participants in the Intensive Venous Blood PK Analysis Set with available data were analyzed.

Cmax is defined as the maximum observed concentration of drug in plasma.

Participants in the Intensive Venous Blood PK Analysis Set were analyzed.