- Condition Centers
Ms. Terrie is a clinical pharmacy writer based in Haymarket, Virginia.
In the United States, annual epidemics of influenza usually occur during the fall or winter months, but the peak of influenza activity can occur as late as April or May.1 According to statistics from the Centers for Disease Control and Prevention (CDC), each year in the United States an estimated 5% to 20% of the population gets influenza and more than 200,000 people are hospitalized from flu complications.1-3 Furthermore, an estimated 36,000 people die annually from complications of influenza, and approximately 90% of those deaths affect individuals 65 years and older.1,3,4
On July 17, 2008, the CDC released Prevention and Control of Influenza Recommendations from the Advisory Committee on Immunization Practices (ACIP) regarding the use of influenza vaccine and antiviral agents. The 2008 recommendations included the 5 following principal updates or changes1:
Certain patient populations, such as the elderly, pediatric patients, pregnant women, and individuals with certain medical conditions (eg, asthma, diabetes, or cardiovascular disease), are more susceptible to developing complications.3,5 Complications of the flu can include bacterial infections, such as pneumonia, otitis media, sinus infections, and dehydration, and can exacerbate certain medical conditions (eg, congestive heart failure, asthma, and diabetes).3,5
The incubation period of the flu can range from 1 to 4 days. The onset of flu symptoms can be mild or severe. The typical influenza symptoms in adults may include abrupt onset of chills, headache, high fever, fatigue, dry cough, sore throat, rhinorrhea, and generalized aches and pains, especially in the back and legs.5-7 Gastrointestinal symptoms, such as nausea, vomiting, and diarrhea also may occur.5-7
The influenza virus can be transmitted via airborne transmission of respiratory droplets, direct contact with an infected person, or through contact with contaminated objects.5,6 Many healthy individuals can transmit the flu to other individuals beginning on the first day prior to the development of symptoms and up to 5 days after becoming sick.5-7
For individuals who wish to decrease their risk of getting influenza, the single best method for preventing influenza is through yearly vaccination, as is recommended by the ACIP and the CDC. Moreover, the ACIP recommends that certain patient populations receive the flu vaccination each year, including individuals at high risk for developing complications from the flu, like children aged 6 months to 18 years; pregnant women; people aged 50 years and older, or those of any age with certain chronic medical conditions; individuals with sickle cell anemia and other hemoglobinopathies; people who have a weakened immune system; and people who receive longterm treatment with steroids for any condition; as well as people who live with or care for those at high risk for developing complications from the flu.1,6,8-11
Certain patient populations should not be vaccinated until they have consulted with their primary health care provider, including individuals with severe allergy to chicken eggs; those who have had a severe reaction to an influenza vaccination in the past; individuals who developed Guillain-Barr? syndrome within 6 weeks of getting a previous influenza vaccine; and individuals who have a moderate or severe illness with a fever. In addition, influenza vaccine is not approved for use in children younger than 6 months of age.1,6,8,10
According to the CDC, each year the seasonal influenza vaccine contains 3 influenza virus strains—one influenza A (H3N2) virus, one influenza A (H1N1) virus, and one influenza B virus. The viruses used in creating flu vaccine are selected each year based on information gathered over the previous year about the strains of flu viruses that are infecting humans and how they are changing.8,9 For the recommended vaccine for the 2008-2009 flu season, all 3 vaccine virus strains were changed from the 2007-2008 season.11 Both TIV and LAIV prepared for the 2008-2009 flu season include A/Brisbane/59/2007 (H1N1)-like, A/Brisbane/10/2007 (H3N2)-like, and B/Florida/4/2006-like antigens.1,12 Approximately 2 weeks after an individual is vaccinated, antibodies develop that protect against the virus.7,8
As noted previously, 2 types of influenza vaccine are available. The TIV is administered via intramuscular injection and is also commonly known as the flu shot. The flu shot is approved for use in individuals older than 6 months, including healthy people and those with chronic medical conditions. Adults and older children should be vaccinated in the deltoid muscle; whereas infants and young children should be vaccinated in the anterolateral aspect of the thigh.1,13
The second type of vaccine is the LAIV. LAIV is approved for use in healthy, nonpregnant individuals, aged 2 to 49 years.12,14,15 The LAIV may be administered in individuals with minor illness. If nasal congestion is present, the delivery of the vaccine to the nasal lining may be limited; therefore it is suggested that vaccination should be delayed until nasal congestion is reduced.13,14 Common adverse effects in children and adolescents include nasal congestion, fever, and headaches. Common adverse effects in adults include sore throat, fatigue, fever, and chills.12,13,15
Although yearly vaccination with the flu vaccine is the primary strategy for preventing the influenza virus, antiviral medications with activity against influenza viruses can be effective for the prevention and treatment of influenza (Table14-20).
The 2 FDA-approved antiviral influenza medications available for use in the United States for the 2008-2009 season are oseltamivir (Tamiflu; Roche) and zanamivir (Relenza; GlaxoSmithKline).18 These agents are classified as neuraminidase inhibitors that have activity against both the A and B viruses.18
In addition, the CDC recommends against the use of the adamantanes for the treatment or prevention of influenza in the United States during the 2008-2009 influenza season, due to an increase in drug resistance.1 For information on this issue, please visit the CDC's Web site at www.cdc.gov/flu/professionals/antivirals/agents.htm.
Each year, before flu season begins, pharmacists can assist their patients by reminding them to get their flu vaccinations, especially those patients in high-risk groups. Patients also should be reminded about practicing good infection control procedures, such as routine hand washing. In general, the majority of individuals who get the flu will typically recover fully within 1 to 2 weeks without complications.
In an effort to stress the importance of getting vaccinated, the CDC has announced that December 8-14, 2008, is National Influenza Vaccination Week. For more information on the influenza virus and the 2008-2009 influenza season, please visit the CDC Web site at www.cdc.gov/flu/