A Study to Evaluate the Efficacy and Safety of Pimodivir in Combination With the Standard-of-Care Treatment in Adolescent, Adult, and Elderly Non-Hospitalized Participants With Influenza A Infection Who Are at Risk of Developing Complications

Present to the clinic with symptoms suggestive of a diagnosis of acute influenza and have at least 1 respiratory symptom and at least 1 systemic symptom, both scored as at least "moderate" if the symptom did not pre-exist before influenza onset, or scored worse than usual if the symptom pre-existed as determined by subject's ratings on Module 1 of the Flu-iiQ and the Pre-existing Symptom Questionnaire in the ePRO device. Symptoms must include the following by category: a) Respiratory symptoms: cough, sore throat, nasal congestion b) Systemic symptoms: headache, body aches or pain, feverishness, fatigue

Tested positive for influenza A infection after the onset of symptoms, using a rapid influenza diagnostic test (RIDT) or, if available, a polymerase chain reaction (PCR)-based or other rapid molecular diagnostic assay

Not be in need of hospitalized medical care at screening. Emergency room or hospital observation status for an anticipated duration of less than (\<)24 hours is not considered hospitalization as long as a determination of the need for hospitalization has not been made

Enrollment and initiation of study drug treatment less than or equal to (\<=)72 hours after onset of influenza symptoms

Participants 13 to 65 years of age, inclusive must also have at least 1 of the following: a) Cardiovascular or cerebrovascular disease (including congenital heart disease, chronic heart failure, coronary artery disease, or stroke; excluding isolated hypertension); b) Chronic lung disease (for example, asthma, chronic obstructive lung disease \[COPD\] or cystic fibrosis); c) Weakened immune system due to disease or medication (for example, participants with human immunodeficiency virus \[HIV\], cancer, or chronic liver or kidney disease \[presence of kidney damage for \>3 months, defined by structural or functional abnormalities of the kidney, with or without decreased GFR manifested by: pathological abnormalities; OR markers of kidney damage, including abnormalities in the composition of the blood or urine or abnormalities in imaging tests\], or participants taking chronic systemic steroids)

What this study is about