Solicited influenza symptoms included cough, nasal congestion, sore throat, aches and pains, fatigue (tiredness), headache, chills/sweats (feeling feverish).

As-treated population included all participants who were randomized and received any portion of their protocol-specified treatment regimen.

Solicited influenza symptoms included cough, nasal congestion, sore throat, aches and pains, fatigue (tiredness), headache, chills/sweats (feeling feverish).

As-treated population included all participants who were randomized and received any portion of their protocol-specified treatment regimen.

An adverse event (AE) is any untoward medical occurrence attributed to study drug in a participant who received study drug. Treatment-emergent events were between administration of study drug and Day 28 that were absent before treatment or that worsened relative to pre-treatment state.

As-treated population included all participants who were randomized and received any portion of their protocol-specified treatment regimen.

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. Treatment-emergent events were between administration of study drug and Day 101 that were absent before treatment or that worsened relative to pre-treatment state.

As-treated population included all participants who were randomized and received any portion of their protocol-specified treatment regimen.

An AE is any untoward medical occurrence attributed to study drug in a participant who received study drug. An AESI was one of scientific and medical interest specific to understanding of the study drug and may have required close monitoring and rapid communication by the investigator to the sponsor. Treatment-emergent events were between administration of study drug and Day 101 that were absent before treatment or that worsened relative to pre treatment state.

As-treated population included all participants who were randomized and received any portion of their protocol-specified treatment regimen.

Quantitative real-time polymerase chain reaction (qRT-PCR) was used to measure influenza viral shedding from the nasopharyngeal swabs. Percentage of participants who shed influenza virus are reported.

Per-protocol (PP) population included all randomized participants who received any portion of their protocol-specified treatment regimen with valid assay results from nasopharyngeal specimens obtained at any post-dosing time point. Participants without confirmed influenza A at baseline were excluded from the PP population.

qRT-PCR was used to measure influenza viral shedding from the nasopharyngeal swabs.

PP population included all randomized participants who received any portion of their protocol-specified treatment regimen with valid assay results from nasopharyngeal specimens obtained at any post-dosing time point. Participants without confirmed influenza A at baseline were excluded from the PP population.

Number of days of viral shedding for participants who shed influenza virus is reported. qRT-PCR was used to measure influenza viral shedding from the nasopharyngeal swabs.

PP population. Participants without confirmed influenza A at baseline were excluded from the PP population. Participants with shedding data available for Day 1 to Day 7 and Day 9 to Day 13 were analyzed for this outcome measure.

Genotypic analysis was performed to identify all amino acid changes in MEDI8852 binding site between each baseline (Day1) sample and the participant's corresponding last sample sequenced. Percentage of participants with changes in the amino acid corresponding to MEDI8852 binding site is reported. Due to the fact that the percentage of participants with amino acid changes in MEDI8852 binding site was zero across all participant samples analyzed, no additional per arm analyses were performed.

PP population. Participants without confirmed influenza A at baseline were excluded from the PP population. Participants with confirmed Influenza A positive and Influenza A concentrations greater than the lower limit of quantification (LLOQ) were analyzed.

Viral susceptibility to MEDI8852 was measured by a Madin-Darby canine kidney (MDCK) cell-based microneutralization assay (Virospot) for viruses recovered from baseline samples and viruses recovered from samples following treatment that contain amino acid changes within the MEDI8852 binding site. Participants with detectable levels (50% tissue culture infectious dose [TCID50]) of virus were considered susceptible and were reported. Due to the fact that the number of participants with viral susceptibility to MEDI8852 binding site was zero across all participant samples analyzed, no additional per arm analyses were performed.

PP population. Participants without confirmed influenza A at baseline were excluded from the PP population. Participants with quantifiable Influenza A (greater than LLOQ) and a unique hemagglutinin gene sequence were analyzed.

Genotypic analysis was performed to identify all amino acid changes in neuraminidase (NA) gene between each baseline (Day1) sample and the participant's corresponding last sample sequenced. Percentage of participants with virus containing known oseltamivir resistance-associated mutations (change in the NA genes) is reported. Due to the fact that the percentage of participants with virus containing known oseltamivir resistance-associated mutation was zero across all participant samples analyzed, no additional per arm analyses were performed.

PP population. Participants without confirmed influenza A at baseline were excluded from the PP population. Participants with confirmed Influenza A positive and Influenza A concentrations greater than the LLOQ were analyzed.