Antiviral medications with activity against influenza viruses are an important adjunct to influenza vaccine in the control of influenza.
| Antiviral agent | Activity against | Use | FDA approved for | Not recommended for use in (Contraindications) | Side Effects |
|---|---|---|---|---|---|
| Zanamivir (Relenza®) | Influenza A and B | Treatment | 7 yrs and older | people with underlying respiratory disease (e.g., asthma, COPD) or heart disease | Allergic reactions: oropharyngeal or facial edema. Side Effects: diarrhea, nausea, sinusitis, nasal signs and symptoms, bronchitis, cough, headache, dizziness, and ear, nose and throat infections. |
| Chemo- prophylaxis | 5 yrs and older | ||||
| Oseltamivir (Tamiflu®) | Influenza A and B | Treatment | 1 yr and older | none | Side Effects: nausea, vomiting. Transient neuropsychiatric events (self injury or delirium) mainly reported among Japanese adolescents and adults. |
| Chemo- prophylaxis | 1 yr and older | none |
When started within the first two days of onset of influenza illness, an influenza antiviral medication can reduce illness severity and shorten the duration of fever and symptoms. In clinical trials conducted among previously healthy outpatients with uncomplicated influenza, treatment with neuraminidase inhibitor antiviral drugs was found to reduce illness by 1-2 days. Studies indicate that influenza antiviral medications may also reduce the risk of serious influenza-related complications (e.g., pneumonia, respiratory failure, exacerbation of chronic diseases and death). When clinically indicated, influenza antiviral medications should be started as soon as possible after symptom onset, ideally within 48 hours of symptom onset. Treatment should not wait for laboratory confirmation of influenza.
Antiviral treatment started after 48 hours of symptom onset may still be beneficial in patients with severe or progressive illness, such as among persons hospitalized with influenza-related illness. Recent data indicate benefit of treatment with a neuraminidase inhibitor for people at higher risk for influenza complications or people with more severe illness in preventing influenza-related complications and deaths, even when started more than 48 hours after illness onset. For example, treatment of pregnant women with influenza has been shown to be most beneficial in preventing respiratory failure and death when started within less than 3 days of illness onset, but still provided benefit when started 3 through 4 days after onset compared to 5 or more days (Siston, et al JAMA 2009).
The following recommendations provide clinical indications of how neuraminidase inhibitor antiviral medications can be used to treat influenza when influenza activity is present in your community.
Antiviral treatment is recommended as early as possible for any patient with confirmed or suspected influenza who:
Clinical judgment, based on the patient"e;s disease severity and progression, age, underlying medical conditions, likelihood of influenza, and time since onset of symptoms, is important to consider when making antiviral treatment decisions for high-risk outpatients. When indicated, antiviral treatment should be started as soon as possible after illness onset.
Antiviral treatment also can be considered for any previously healthy, non high risk, symptomatic outpatient with confirmed or suspected influenza based upon clinical judgment, if treatment can be initiated within 48 hours of illness onset.
Note: Recommended antiviral medications (neuraminidase inhibitors) are not licensed for treatment of children ≤1 year of age for oseltamivir or children aged ≤7 years for zanamivir. Oseltamivir was used for treatment of 2009 pandemic influenza A (H1N1) virus infection in children ≤1 year of age under an Emergency Use Authorization (EUA), but this EUA has expired. Limited information on use of oseltamivir for children from birth to 1 year is available.
*While children aged ≤5 years are considered to be at higher risk for influenza-related complications, the risk is highest among children aged ≤2 years old.
**The likelihood of influenza virus infection in a patient depends upon the prevalence of influenza activity in the local community, and the patient"e;s signs and symptoms. Information about influenza activity in the United States during the influenza season is available at www.cdc.gov/flu and http://www.cdc.gov/flu/weekly/fluactivitysurv.htm. For information on local community influenza activity, clinicians should contact their local and state health departments.
Confirmation of influenza virus infection may be performed by different influenza testing methods. Information on influenza testing is available at: www.cdc.gov/flu/professionals/diagnosis/.
In areas with limited antiviral medication availability, local public health authorities might provide additional guidance about prioritizing treatment within groups at higher risk for complications. Current CDC guidance on treatment of influenza should be consulted, and updated recommendations from CDC can be found at http://www.cdc.gov/flu/.
| Antiviral Agent | Use | Children | Adults |
|---|---|---|---|
| Zanamivir (Relenza®) | Treatment | 10 mg (2 inhalations) twice daily | 10 mg (2 inhalations) twice daily |
| Chemo prophylaxis | 10 mg (2 inhalations) once daily | 10 mg (2 inhalations) once daily | |
| Oseltamivir (Tamiflu®) | Treatment | (Not FDA approved for use in children <1 yr old, but was approved under EUA during the 2009 H1N1 pandemic) If <1 yr old, the dose is 3 mg/kg/dose twice daily | 75 mg twice daily |
| (Dose varies by child"e;s weight) If ≥1 yr old and weigh 15 kg or less, the dose is 30 mg twice a day. | |||
| If ≥1 yr old and weigh ≥15 to 23 kg, the dose is 45 mg twice a day. | |||
| If ≥1 yr old and weigh ≥23 to 40 kg, the dose is 60 mg twice a day. | |||
| If ≥1 yr old and weigh more than 40 kg, the dose is 75 mg twice a day. | |||
| Chemo prophylaxis | (Not FDA approved for use in children <1 yr old) If child is <3 months old, chemoprophylactic use is not recommended unless situation is judged critical due to limited data on use in this age group. | 75 mg once daily | |
| (Not FDA approved for children <1 yr, but use in children ≥3 months and <1 yr old was approved under EUA during the 2009 H1N1 pandemic) If child ≥3 months and <1 yr old, dose is 3 mg/kg/dose once per day. | |||
| (Dose varies by child"e;s weight) If ≥1 yr old, and weigh 15 kg or less, the dose is 30 mg once a day. | |||
| If ≥1 yr old and weigh ≥15 to 23 kg, the dose is 45 mg once a day. | |||
| If ≥1 yr old and weigh ≥23 to 40 kg, the dose is 60 mg once a day. | |||
| If ≥1 yr old and weigh more than 40 kg, the dose is 75 mg once a day. |
| Treatment | Recommended duration for antiviral treatment is 5 days. Longer treatment courses for patients who remain severely ill after 5 days of treatment can be considered. |
| Chemo prophylaxis | Recommended duration is 7 days after exposure. For control of outbreaks in long-term care facilities and hospital, CDC recommends antiviral chemoprophylaxis for a minimum of 2 weeks, including in vaccinated persons, and up to 1 week after the last known case was identified. |
Annual influenza vaccination is the best way to prevent influenza because vaccination can be given well before influenza virus exposures occur, and can provide safe and effective immunity throughout the influenza season. However, antiviral medications are 70% to 90% effective in preventing influenza and are useful adjuncts to vaccination. To be effective as chemoprophylaxis, an antiviral medication must be taken each day for the duration of potential exposure to a person with influenza or until immunity after vaccination develops (antibody development after vaccination takes about two weeks in adults and can take longer in children depending on age and vaccination history). Chemoprophylaxis generally is not recommended if more than 48 hours have elapsed since the last exposure to an infectious person. Patients receiving chemoprophylaxis should be encouraged to seek medical evaluation as soon as they develop a febrile respiratory illness that might indicate influenza. CDC does not recommend widespread or routine use of antiviral medications for chemoprophylaxis so as to limit the possibilities that antiviral resistant viruses could emerge. Indiscriminate use of chemoprophylaxis might promote resistance to antiviral medications, or reduce antiviral medication availability for treatment of persons at higher risk for influenza complications or those who are severely ill. An emphasis on early treatment and monitoring is an alternative to chemoprophylaxis after a suspected exposure for some persons.
However, prophylactic use of antiviral medications to control outbreaks among high risk persons in institutional settings is recommended. For example, when influenza is identified as a cause of respiratory outbreak among nursing home residents, use of prophylaxis for all residents and for unvaccinated health care staff is recommended. For more information on the control of institutional outbreaks, please see the IDSA guidelines: www.idsociety.org/content.aspx?id=9202#flu
The following are examples of how antiviral medications can be considered for chemoprophylaxis to prevent influenza:
For more information, visit www.cdc.gov/flu, or call CDC at 800-CDC-INFO (English and Spanish) or 888-232-6348 (TTY).