The percentage of participants with adverse events (AEs) and serious adverse events (SAEs) following administration of a single dose of IV VIS410.

Safety Population The safety population included all subjects randomized who received IV study drug. The safety population summaries were based on the actual treatment received.

Percentage of participants experiencing any TEAE, TEAEs considered related to study treatment and the number of participants experiencing adverse events of special interest (AESI). A TEAE is defined as an adverse event that starts on or after the date of study drug IV infusion. AESIs included hypersensitivity reaction, anaphylactic reaction, or injection site adverse event.

Safety Population. The safety population included all participants randomized who received IV study drug. The safety population summaries were based on the actual treatment received.

The Influenza Patient Reported Outcome (FluPRO) questionnaire is a 32-question instrument that assesses the occurrence and intensity of influenza associated symptoms (scale of 0 to 4, with 0 representing no symptoms) over 24 hours (lower scores indicate better outcomes). FluPRO data were recorded by subjects at Baseline (Day 1), then daily thereafter through Day 10. These data were summarized at each visit by treatment group. The data below show the percent change in mean total symptom scores over time by treatment arm.

Modified Intent-to-Treat Population. The modified intent-to-treat (mITT) population included all subjects who received IV study drug and were confirmed influenza A positive by a molecular test at the central virological laboratory.

Number of participants requiring hospitalization for influenza-related complications

Modified Intent-to-Treat Population The modified intent-to-treat (mITT) population included all subjects who received IV study drug and were confirmed influenza A positive by a molecular test at the central virological laboratory.

Duration of hospitalization for participants with at least 1 complication of influenza. There were no participants hospitalized for complications of influenza.

Modified Intent-to-Treat Population. The modified intent-to-treat (mITT) population included all subjects who received IV study drug and were confirmed influenza A positive by a molecular test at the central virological laboratory.

Count of participants with at least 1 complication of influenza

Modified Intent-to-Treat Population. The modified intent-to-treat (mITT) population included all subjects who received IV study drug and were confirmed influenza A positive by a molecular test at the central virological laboratory.

Number of participants with influenza A relapse/reinfection

Modified Intent-to-Treat Population The modified intent-to-treat (mITT) population included all subjects who received IV study drug and were confirmed influenza A positive by a molecular test at the central virological laboratory.

The maximum observed concentration of VIS410 in serum (Cmax).

The Pharmacokinetics (PK) population included all subjects who received IV study drug and had at least 1 PK concentration that could be calculated

Time corresponding to the maximum serum concentration of VIS410.

The PK population included all subjects who received IV study drug and had at least 1 PK concentration that could be calculated

VIS410 area under the plasma concentration time curve in serum. AUC 0-infinity is from the time of dosing extrapolated to infinity.

The PK population included all subjects who received IV study drug and had at least 1 PK concentration that could be calculated

VIS410 area under the plasma concentration time curve in serum. AUC 0-last is the area under the plasma concentration time curve from time 0 to the last measurable concentration.

The PK population included all subjects who received IV study drug and had at least 1 PK concentration that could be calculated

Terminal elimination half-life of VIS410 in serum (t1/2) in serum.

The PK population included all subjects who received IV study drug and had at least 1 PK concentration that could be calculated

Summary of VIS410 total clearance (CL) in serum.

The PK population included all subjects who received IV study drug and had at least 1 PK concentration that could be calculated.

The difference between VIS410 and placebo treatment groups in viral AUC based on the half-maximal tissue culture infective dose (TCID50) from nasopharyngeal swab samples taken from the first 50 participants.

Modified Intent-to-Treat Population The modified intent-to-treat (mITT) population included all subjects who received IV study drug and were confirmed influenza A positive by a molecular test at the central virological laboratory.

The difference between VIS410 and placebo treatment groups in peak viral load based on the half-maximal tissue culture infective dose (TCID50) from nasopharyngeal swab samples taken from the first 50 participants.

Modified Intent-to-Treat Population The modified intent-to-treat (mITT) population included all subjects who received IV study drug and were confirmed influenza A positive by a molecular test at the central virological laboratory.

The number of days for the median time to resolution of peak viral load from end of infusion by nasopharyngeal swabs collected from the first 50 participants and tested by half maximal tissue culture infective dose (TCID50)

Modified Intent-to-Treat Population The modified intent-to-treat (mITT) population included all subjects who received IV study drug and were confirmed influenza A positive by a molecular test at the central virological laboratory.

Count of subjects testing positive for anti-VIS410 antibodies on days 1, 14, 56 and 100. A positive result includes samples confirmed positive and above titer cut point factor (and titer ≥ 1). Negative results include screened or confirmed negative or confirmed positive but below titer cut point factor (titer < 1). For participants receiving placebo, only samples from two participants were tested at Days 14 and 56.

Safety Population The safety population included all ITT subjects who received IV study drug. The safety population summaries were based on the actual treatment received. Not all participants had samples for all timepoints. For participants receiving placebo, all participants were tested on Day 1 and Day 100; only samples from two participants were tested at Days 14 and 56.

The Influenza Patient Reported Outcome (FluPRO) questionnaire is a 32-question instrument that assesses the occurrence and intensity of influenza associated symptoms (scale of 0 to 4, with 0 representing no symptoms) over 24 hours (lower scores indicate better outcomes). FluPRO data were recorded by subjects at Baseline (Day 1), then daily thereafter through Day 10. Data below show the time to symptom resolution for Total Symptom Score.

Modified Intent-to-Treat Population. The modified intent-to-treat (mITT) population included all subjects who received IV study drug and were confirmed influenza A positive by a molecular test at the central virological laboratory.