Clinical Overview of Influenza

Clinical Overview of Influenza

In all patients, the flu can take its toll.

  • On average, influenza infects an estimated 5 to 20 percent (16-64 million) of the United States population annually.1,2 The severity of influenza is unpredictable and often underestimated.

The severity of influenza is unpredictable and often underestimated.

  • Annual deaths associated with seasonal influenza is estimated to range from 3,000 to 49,000.3
  • Approximately 90% of influenza-associated deaths occur among adults aged ≥65 years.3

Flu is a major cause of hospitalization.

  • According to the CDC, on average, more than 200,000 people are hospitalized each year with influenza-related infections.4
  • Annual incidence of hospitalizations ranged from 157,911 in 1990-1991 to 430,960 in 1997-1998.4

Links to cdc.gov and references to CDC are provided for informational purposes only. CDC does not endorse private products, services or enterprises.

Symptoms of influenza

Influenza is thought to spread from person to person through respiratory droplets that are dispersed when an infected person coughs or sneezes in close proximity to someone who is not infected.1

The typical incubation period for influenza is 1-4 days (average: 2 days).1,5

Adults can be infectious from 1 day before onset of symptoms to 5-7 days after illness onset.5

Uncomplicated influenza is characterized by abrupt onset of signs and symptoms that may include6,7:

  • Fever
  • Chills
  • Myalgia
  • Headache
  • Tiredness
  • Sore throat
  • Runny or stuffy nose
  • Chest discomfort, cough
  • Some people may have vomiting and diarrhea, though this is more common in children than adults
  • Most people who get influenza will recover in a few days to less than 2 weeks8

Did You Know?

Did you know? In a clinical study, Tamiflu prophylaxis reduced postexposure flu transmission in children aged 1-12 years by 82%.9

Learn more >


References

  1. Thompson W, Shay D, Weintraub E, et al. Influenza-Associated Hospitalizations in the United States. JAMA. 2004;292(11):1333-1340. doi:10.1001/jama.292.11.1333.
  2. US Census Bureau. U.S. and World Population Clock. http://www.census.gov/popclock/. Accessed October 1, 2015.
  3. Centers for Disease Control and Prevention. Estimating Seasonal Influenza-Associated Deaths in the United States: CDC Study Confirms Variability of Flu. http://www.cdc.gov/flu/about/disease/us_flu-related_deaths.htm. Updated March 18, 2015. Accessed December 14, 2015.
  4. Centers for Disease Control and Prevention. Seasonal Influenza–Associated Hospitalizations in the United States: Questions & Answers. http://www.cdc.gov/flu/about/qa/hospital.htm. Updated May 26, 2016. Accessed August 2, 2016.
  5. Centers for Disease Control and Prevention. How Flu Spreads. http://www.cdc.gov/flu/about/disease/spread.htm. Updated September 12, 2013. Accessed December 14, 2015.
  6. Centers for Disease Control and Prevention. Key Facts about Influenza (Flu) & Flu Vaccine. http://www.cdc.gov/flu/keyfacts.htm. Updated August 7, 2015. Accessed October 1, 2015.
  7. National Institute of Allergy and Infectious Diseases. Is It a Cold or the Flu? https://www.niaid.nih.gov/topics/Flu/Documents/sick.pdf. Updated August 2014. Accessed October 1, 2015.
  8. Centers for Disease Control and Prevention. Flu Symptoms & Severity. http://www.cdc.gov/flu/about/disease/symptoms.htm. Updated August 19, 2015. Accessed October 1, 2015.
  9. Hayden FG, Belshe R, Villanueva C, et al. Management of influenza in households: a prospective, randomized comparison of oseltamivir treatment with or without postexposure prophylaxis. J Infect Dis. 2004;189:440-449.

Indications

TAMIFLU is indicated for the treatment of acute, uncomplicated illness due to influenza A and B infection in patients 2 weeks of age and older who have been symptomatic for no more than 48 hours. TAMIFLU is indicated for the prophylaxis of influenza A and B in patients 1 year and older.

  • TAMIFLU is not a substitute for early influenza vaccination on an annual basis as recommended by the Centers for Disease Control and Prevention Advisory Committee on Immunization Practices.
  • Influenza viruses change over time. Emergence of resistance substitutions could decrease drug effectiveness. Other factors (for example, changes in viral virulence) might also diminish clinical benefit of antiviral drugs. Prescribers should consider available information on influenza drug susceptibility patterns and treatment effects when deciding whether to use TAMIFLU.
  • TAMIFLU is not recommended for patients with end-stage renal disease not undergoing dialysis.

Important Safety Information

Serious Skin/Hypersensitivity Reactions

  • Tamiflu is contraindicated in patients who have had severe allergic reactions such as anaphylaxis or serious skin reactions such as toxic epidermal necrolysis, Stevens- Johnson syndrome, or erythema multiforme to Tamiflu or any component of the product.
  • In postmarketing experience, cases of anaphylaxis and serious skin reactions, including toxic epidermal necrolysis, Stevens-Johnson syndrome, and erythema multiforme, have been reported with Tamiflu. Tamiflu should be stopped and appropriate treatment instituted if an allergic-like reaction occurs or is suspected.

Neuropsychiatric Events

  • Influenza can be associated with a variety of neurologic and behavioral symptoms, which can include events such as hallucinations, delirium and abnormal behavior, in some cases resulting in fatal outcomes. These events may occur in the setting of encephalitis or encephalopathy but can occur without obvious severe disease.
  • There have been postmarketing reports (mostly from Japan) of delirium and abnormal behavior leading to injury, and in some cases resulting in fatal outcomes, in patients with influenza who were receiving Tamiflu. Because these events were reported voluntarily during clinical practice, estimates of frequency cannot be made but they appear to be uncommon based on Tamiflu usage data. These events were reported primarily among pediatric patients and often had an abrupt onset and rapid resolution. The contribution of Tamiflu to these events has not been established. Closely monitor Tamiflu-treated patients with influenza for signs of abnormal behavior. If neuropsychiatric symptoms occur, evaluate the risks and benefits of continuing treatment for each patient.

Risk of Bacterial Infections

  • There is no evidence for efficacy of Tamiflu in any illness caused by pathogens other than influenza viruses. Serious bacterial infections may begin with influenza-like symptoms or may coexist with or occur as complications during the course of influenza. Tamiflu has not been shown to prevent such complications.

Fructose Intolerance in Patients with Hereditary Fructose Intolerance

  • Fructose can be harmful to patients with hereditary fructose intolerance. One dose of 75 mg Tamiflu for oral suspension delivers 2 grams of sorbitol. This is above the daily maximum limit of sorbitol for patients with hereditary fructose intolerance, and may cause dyspepsia and diarrhea.

Use in Specific Populations

  • Efficacy of Tamiflu in the treatment of influenza in patients with chronic cardiac disease and/or respiratory disease was evaluated in one randomized, placebo-controlled clinical trial. Efficacy in this population was not established, but no new safety signals were identified.
  • No clinical trial data are available regarding treatment of influenza in patients with any medical condition sufficiently severe or unstable to be considered at imminent risk of requiring hospitalization.
  • Efficacy of Tamiflu for treatment or prophylaxis of influenza has not been established in immunocompromised patients
  • Safety and efficacy of Tamiflu for treatment of influenza in pediatric patients less than 2 weeks of age have not been established
  • Safety and efficacy of Tamiflu for prophylaxis of influenza have not been established for pediatric patients less than 1 year of age

Concurrent Use with Live Attenuated Influenza Vaccine

  • The concurrent use of Tamiflu with live attenuated influenza vaccine (LAIV) intranasal has not been evaluated. However, because of the potential for Tamiflu to inhibit replication of live vaccine virus and possibly reduce the efficacy of LAIV, avoid administration of LAIV within 2 weeks before or 48 hours after administration of Tamiflu, unless medically indicated.

Most Common Adverse Reactions

  • Adverse reactions that occurred in ≥ 1% of Tamiflu-treated adults and adolescents (13 years of age and older) and ≥ 1% greater in Tamiflu-treated subjects when compared to placebo-treated subjects were:
    • Pooled treatment trials - nausea (10%, 6%), vomiting (8%, 3%), headache (2%, 1%)
    • Pooled prophylaxis trials- nausea (8%, 4%), vomiting (2%, 1%), headache (17%, 16%) pain (4%, 3%)
  • Pediatric subjects 1 to 12 years of age: In the treatment trials, vomiting was the only adverse reaction reported at a frequency of ≤1% in subjects receiving Tamiflu (16%) compared to placebo (8%). In the prophylaxis trials, vomiting was the most frequent adverse reaction (8% Tamiflu versus 2% in the no prophylaxis group).
  • The safety profile observed in pediatric patients 2 weeks to less than 1 year of age was similar across the age range studied, with vomiting (9%), diarrhea (7%) and diaper rash (7%) being the most frequently reported adverse reactions

For additional important safety information, please see Tamiflu full prescribing information at www.tamiflu.com.

You are encouraged to report side effects to Genentech by calling 1-888-835-2555 or to the FDA by visiting www.fda.gov/medwatch or calling 1-800-FDA-1088.

Indications and Important Safety Information

Indications

TAMIFLU is indicated for the treatment of acute, uncomplicated illness due to influenza A and B infection in patients 2 weeks of age and older who have been symptomatic for no more than 48 hours. TAMIFLU is indicated for the prophylaxis of influenza A and B in patients 1 year and older.

  • TAMIFLU is not a substitute for early influenza vaccination on an annual basis as recommended by the Centers for Disease Control and Prevention Advisory Committee on Immunization Practices.
  • Influenza viruses change over time. Emergence of resistance substitutions could decrease drug effectiveness. Other factors (for example, changes in viral virulence) might also diminish clinical benefit of antiviral drugs. Prescribers should consider available information on influenza drug susceptibility patterns and treatment effects when deciding whether to use TAMIFLU.
  • TAMIFLU is not recommended for patients with end-stage renal disease not undergoing dialysis.

Important Safety Information

Serious Skin/Hypersensitivity Reactions

  • Tamiflu is contraindicated in patients who have had severe allergic reactions such as anaphylaxis or serious skin reactions such as toxic epidermal necrolysis, Stevens- Johnson syndrome, or erythema multiforme to Tamiflu or any component of the product.
  • In postmarketing experience, cases of anaphylaxis and serious skin reactions, including toxic epidermal necrolysis, Stevens-Johnson syndrome, and erythema multiforme, have been reported with Tamiflu. Tamiflu should be stopped and appropriate treatment instituted if an allergic-like reaction occurs or is suspected.

Neuropsychiatric Events

  • Influenza can be associated with a variety of neurologic and behavioral symptoms, which can include events such as hallucinations, delirium and abnormal behavior, in some cases resulting in fatal outcomes. These events may occur in the setting of encephalitis or encephalopathy but can occur without obvious severe disease.
  • There have been postmarketing reports (mostly from Japan) of delirium and abnormal behavior leading to injury, and in some cases resulting in fatal outcomes, in patients with influenza who were receiving Tamiflu. Because these events were reported voluntarily during clinical practice, estimates of frequency cannot be made but they appear to be uncommon based on Tamiflu usage data. These events were reported primarily among pediatric patients and often had an abrupt onset and rapid resolution. The contribution of Tamiflu to these events has not been established. Closely monitor Tamiflu-treated patients with influenza for signs of abnormal behavior. If neuropsychiatric symptoms occur, evaluate the risks and benefits of continuing treatment for each patient.

Risk of Bacterial Infections

  • There is no evidence for efficacy of Tamiflu in any illness caused by pathogens other than influenza viruses. Serious bacterial infections may begin with influenza-like symptoms or may coexist with or occur as complications during the course of influenza. Tamiflu has not been shown to prevent such complications.

Fructose Intolerance in Patients with Hereditary Fructose Intolerance

  • Fructose can be harmful to patients with hereditary fructose intolerance. One dose of 75 mg Tamiflu for oral suspension delivers 2 grams of sorbitol. This is above the daily maximum limit of sorbitol for patients with hereditary fructose intolerance, and may cause dyspepsia and diarrhea.

Use in Specific Populations

  • Efficacy of Tamiflu in the treatment of influenza in patients with chronic cardiac disease and/or respiratory disease was evaluated in one randomized, placebo-controlled clinical trial. Efficacy in this population was not established, but no new safety signals were identified.
  • No clinical trial data are available regarding treatment of influenza in patients with any medical condition sufficiently severe or unstable to be considered at imminent risk of requiring hospitalization.
  • Efficacy of Tamiflu for treatment or prophylaxis of influenza has not been established in immunocompromised patients
  • Safety and efficacy of Tamiflu for treatment of influenza in pediatric patients less than 2 weeks of age have not been established
  • Safety and efficacy of Tamiflu for prophylaxis of influenza have not been established for pediatric patients less than 1 year of age

Concurrent Use with Live Attenuated Influenza Vaccine

  • The concurrent use of Tamiflu with live attenuated influenza vaccine (LAIV) intranasal has not been evaluated. However, because of the potential for Tamiflu to inhibit replication of live vaccine virus and possibly reduce the efficacy of LAIV, avoid administration of LAIV within 2 weeks before or 48 hours after administration of Tamiflu, unless medically indicated.

Most Common Adverse Reactions

  • Adverse reactions that occurred in ≥ 1% of Tamiflu-treated adults and adolescents (13 years of age and older) and ≥ 1% greater in Tamiflu-treated subjects when compared to placebo-treated subjects were:
    • Pooled treatment trials - nausea (10%, 6%), vomiting (8%, 3%), headache (2%, 1%)
    • Pooled prophylaxis trials- nausea (8%, 4%), vomiting (2%, 1%), headache (17%, 16%) pain (4%, 3%)
  • Pediatric subjects 1 to 12 years of age: In the treatment trials, vomiting was the only adverse reaction reported at a frequency of ≤1% in subjects receiving Tamiflu (16%) compared to placebo (8%). In the prophylaxis trials, vomiting was the most frequent adverse reaction (8% Tamiflu versus 2% in the no prophylaxis group).
  • The safety profile observed in pediatric patients 2 weeks to less than 1 year of age was similar across the age range studied, with vomiting (9%), diarrhea (7%) and diaper rash (7%) being the most frequently reported adverse reactions

For additional important safety information, please see Tamiflu full prescribing information at www.tamiflu.com.

You are encouraged to report side effects to Genentech by calling 1-888-835-2555 or to the FDA by visiting www.fda.gov/medwatch or calling 1-800-FDA-1088.

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