Influenza, Influenza-Associated Mortality, and Novel Influenza A

Vaccination

The best way to protect against influenza is to get vaccinated each year. There are three forms of the vaccine, inactivated influenza vaccine (IIV), administered intramuscularly or intradermally, live-attenu ated influenza vaccine (LAIV), administered intranasally, and recombinant influenza vaccine (RIV), a ministered intramuscularly. Influenza vaccines are either trivalent or quadrivalent.  Trivalent vaccines protect against three different influenza viruses, two influenza A viruses and one influenza B virus. Quadrivalent vaccines protect against four different influenza viruses, two influenza A viruses and two influenza B viruses.

The Advisory Committee on Immunization Practices (ACIP) recommends annual influenza vaccination for all persons aged 6 months and older. Persons at high risk of having serious flu- related complications or because they live with or care for high risk persons especially should receive yearly vaccinations. CDC has yearly recommendations for high risk groups. Refer to the Morbidity and Mortality Weekly Report (MMWR), Prevention and Control of Influenza: Recommendations of the Advisory committee on Immunization Practices (ACIP). (This is published annually in April at: http://www.cdc.gov/vaccines/hcp/acip-recs/vacc- specific/flu.html). ACIP does not recommend one vaccine over the other as long as the vaccine is licensed for the appropriate age group. However, in light of low effectiveness against influenza A(H1N1)pdm09 in the United States during the 2013–14 and 2015–16 seasons, for the 2016–17 season, ACIP made the interim recommendation that LAIV4 should not be used. For the most up to date seasonal vaccine information, visit https://www.cdc.gov/flu/protect/ vaccine/index.html.

Education

Take every day preventative actions to stop the spread of influenza.

• Try to avoid contact with sick people.
• If you are sick with influenza-like illness, stay home for at least 24 hours after your fever is gone (without the use of fever-reducing medicine) except to get medical care or for other necessities.
• While sick, limit contact with others as much as possible to keep from infecting them.
• Cover your nose and mouth with a tissue when you cough or sneeze. Throw the tissue in the trash after you use it.
• Wash your hands often with soap and water. If soap and water are not available, use an alcohol-based hand rub.
• Avoid touching your eyes, nose, and mouth.
• Persons at high risk for influenza complications who become ill with influenza-like illness should call their health care provider as soon as possible to determine if they need antiviral treatment. Early treatment (within 48 hours of the onset of illness) with antiviral medications can decrease the risk of severe illness from influenza.

Treatment/Chemoprophylaxis

Influenza antiviral prescription drugs can be used to treat influenza or to prevent illness. In the United States, five licensed antiviral medications are approved for treatment and chemoprophylaxis of influenza. Currently, neuraminidase inhibitors (oseltamivir, zanamivir, peramivir) are the only recommended influenza antiviral drugs because of widespread resistance to the adamantanes (amantadine, rimantadine) among influenza viruses. Antiviral resistance to oseltamivir, zanamivir, and peramivir among circulating influenza viruses is currently low, but this could change. The neuraminidase inhibitors are effective against influenza A and B viruses while the adamantanes are effective only against influenza A viruses. 

Treatment: Early antiviral treatment can shorten the duration of fever and illness symptoms, and may reduce the risk of complications from influenza. Clinical benefit is greatest when antiviral treatment is administered early, especially within 48 hours of influenza illness onset. Decisions about starting antiviral treatment should not wait for laboratory confirmation of influenza. Antiviral treatment is recommended as early as possible for any patient with confirmed or suspected influenza who is hospitalized, has severe, complicated, or progressive illness, or is at higher risk for influenza complications. Persons at higher risk for influenza complications recommended for antiviral treatment include:

• Children aged younger than 2 years
• Adults aged 65 years and older
• Persons with chronic pulmonary (including asthma), cardiovascular (except hypertension alone), renal, hepatic, hematological (including sickle cell disease), and metabolic disorders (including diabetes mellitus), or neurologic and neurodevelopment conditions (including disorders of the brain, spinal cord, peripheral nerve, and muscle, such as cerebral palsy, epilepsy [seizure disorders], stroke, intellectual disability [mental retardation], moderate to severe developmental delay, muscular dystrophy, or spinal cord injury)
• Persons with immunosuppression, including that caused by medications or by human immunodeficiency virus (HIV) infection
• Women who are pregnant or postpartum (within 2 weeks after delivery)
• Persons aged younger than 19 years who are receiving long-term aspirin therapy
• American Indians/Alaska Natives
• Persons who are morbidly obese (i.e., body mass index is equal to or greater than 40)
• Residents of nursing homes and other chronic care facilities 

Chemoprophylaxis: 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. Antiviral medications are approximately 7090 % effective in preventing influenza. Widespread or routine use of antiviral medications for chemoprophylaxis is not recommended so as to limit the possibilities that antiviral resistant viruses could emerge.  Antiviral chemoprophylaxis generally is not recommended if more than 48 hours have elapsed since the first exposure to an infectious person. The following are examples of situations where antiviral medications can be considered for chemoprophylaxis to prevent influenza:

• Prevention of influenza in persons at high risk of influenza complications during the first two weeks following vaccination after exposure to an infectious person
• Prevention for people with severe immune deficiencies or others who might not respond to influenza vaccination, such as persons receiving immunosuppressive medications, after exposure to an infectious person
• Prevention for people at high risk for complications from influenza who cannot receive influenza vaccine due to a contraindication after exposure to an infectious person
• Prevention of influenza among residents of institutions, such as long-term care facilities, during influenza outbreaks in the institution

For current recommendations about treatment and chemoprophylaxis, see http://www.cdc.gov/flu/professionals/antivirals/index.html.