A Study to Evaluate a Single Intramuscular Dose of Motavizumab to Treat Children With Respiratory Syncytial Virus (RSV) Illness

Percentage of Participants Who Have Progression of RSV Illness That Requires Subsequent Hospitalization

The percentage of participants who have progression of RSV illness that requires subsequent hospitalization is reported. RSV illness symptomps included fever, coryza, cough, and parental opinion of return to normal health and activity.

Time frame: From Randomiation (Day 0) Up to Day 30

Respiratory Assessment Change Score (RACS) Derived From Baseline

The RACS assesses changes in wheezing and retractions as measured by the respiratory distress assessment instrument (RDAI) score and changes in respiratory rate. A RDAI score is a measure of the degree of severity of wheezing and retractions, with score range from 0 to 17; higher scores indicate more severe disease. Respiratory rate is summarized by raw scores and standardized change score. Change in respiratory rate of less than or equal to (\<=) 5% from baseline is counted as a change of 0 units and a change in respiratory rate is assigned 1 point per each 10% change in respiratory rate. The RACS is calculated as arithmetic sum of RDAI score change and of the standardized respiratory rate change (for example, a child showing improvement who had a RDAI of -5 and a respiratory rate change of -2 would have a RACS score of -7). The RACS assessment does not have a minimum and/or maximum scale range. A decrease in RACS represents improvement, whereas an increase signifies deterioration.

Time frame: Baseline (Day 0); and Days 2, 7, and 30

Change From Baseline in Oxygen Saturation Level

Change from baseline in oxygen saturation level is reported.

Time frame: Baseline (Day 0), Days 2, 7, and 30

Change in RACS of RSV-infected Outpatient Participants Who Subsequently Required Hospitalization

The RACS assesses changes in wheezing and retractions as measured by the RDAI score and changes in respiratory rate. A RDAI score is a measure of the degree of severity of wheezing and retractions, with score range from 0 to 17; higher scores indicate more severe disease. Respiratory rate is summarized by raw scores and standardized change score. A change in respiratory rate of \<= 5% from baseline is counted as a change of 0 units and a change in respiratory rate is assigned 1 point per each 10% change in the respiratory rate. The RACS is calculated as the arithmetic sum of the RDAI score change and of the standardized respiratory rate change (for example, a child showing improvement who had a RDAI of -5 and a respiratory rate change of -2 would have a RACS score of -7). The RACS assessment does not have a minimum and/or maximum scale range. A decrease in the RACS represents improvement, whereas an increase signifies deterioration.

Time frame: Baseline (Day 0) to Day 30

Oxygen Saturation Levels in RSV-infected Outpatient Participants Who Subsequently Required Hospitalization

Time frame: Baseline (Day 0) to Day 30

Heart Rate of RSV-infected Outpatient Participants Who Subsequently Required Hospitalization

Time frame: Baseline (Day 0) to Day 30

Respiratory Rate of RSV-infected Outpatient Participants Who Subsequently Required Hospitalization

Time frame: Baseline (Day 0) to Day 30

Number of Participants Who Required Hospitalization, Intensive Care Unit (ICU) Stay, Supplemental Oxygen, and Mechanical Ventilation

Number of participants who required hospitalization, ICU stay, supplemental oxygen, and mechanical ventilation is reported.

Time frame: Baseline (Day 0) to Day 90

Duration of Hospitalization, ICU Stay, Supplemental Oxygen Used, and Mechanical Ventilation Required

Time frame: Baseline (Day 0) to Day 90

Number of Participants Who Progresses From Upper Respiratory Tract Infection to Lower Respiratory Tract Infection (LRI)

A LRI event is one that has a medical diagnosis of bronchiolitis or pneumonia. In the absence of such a medical diagnosis, the occurrence of LRI events will be determined by the principal investigator after review of the medical record and based on the presence of retractions or lower respiratory tract rhonchi, wheezing, crackles, or rales in children with a positive RSV test.

Time frame: Baseline (Day 0) to Day 30

Number of LRI Infected Participants Who Required Hospitalization, ICU Stay, Supplemental Oxygen, Mechanical Ventilation, and Respiratory Medications

Number of LRI infected participants who required hospitalization, ICU stay, supplemental oxygen, mechanical ventilation, and respiratory medications are reported.

Time frame: Baseline (Day 0) to Day 30

RACS in Participants With LRI

The RACS assesses changes in wheezing and retractions as measured by RDAI score and changes in respiratory rate. A RDAI score is a measure of degree of severity of wheezing and retractions, with score range from 0 to 17; higher scores indicate more severe disease. Respiratory rate is summarized by raw scores and standardized change score. A change in respiratory rate of \<= 5% from baseline is counted as a change of 0 units and a change in respiratory rate is assigned 1 point per each 10% change in the respiratory rate. The RACS is calculated as the arithmetic sum of the RDAI score change and of the standardized respiratory rate change (for example, a child showing improvement who had a RDAI of -5 and a respiratory rate change of -2 would have a RACS score of -7). The RACS assessment does not have a minimum and/or maximum scale range. A decrease in the RACS represents improvement, whereas an increase signifies deterioration. RACS in participants with LRI is reported.

Time frame: From Baseline (Day 0) to Days 2, 7, and 30

Motavizumab Concentration in Upper Respiratory Tract

Motavizumab concentration in upper respiratory tract (nasal wash aspirates) is reported.

Time frame: Days 0 (pre-dose), 2, and 30

Serum Concentration of Motavizumab

Serum concentration of motavizumab is reported.

Time frame: Days 2, 30, and 90

Numbers of Participants With Positive Anti-Motavizumab Antibodies

The number of participants with positive serum antibodies to motavizumab are reported.

Time frame: Days 0 (pre-dose) and 90

Serum Cytokine Levels

Serum Cytokine Levels are reported.

Time frame: Days 0 (pre-dose), 30, and 90

Nasal Wash Cytokine Levels

Nasal wash cytokine levels are reported.

Time frame: Days 0 (pre-dose), 2, 30, and 90

Number of Participants With Treatment-emergent Adverse Events (TEAEs) and Treatment-emergent Serious Adverse Events (TESAEs)

An adverse event (AE) is any untoward medical occurrence in a participant who received study drug without regard to possibility of causal relationship. A serious adverse event (SAE) is an AE resulting in any of the following outcomes or deemed significant for any other reason: death; initial or prolonged inpatient hospitalization; life threatening experience (immediate risk of dying); persistent or significant disability/incapacity; congenital anomaly. The TEAEs are defined as events present at baseline that worsened in intensity after administration of study drug or events absent at baseline that emerged after administration of study drug.

Time frame: From the administration of study drug (Day 0) through Day 90