Influenza, a highly contagious, airborne respiratory tract infection, is responsible for approximately 36,000 deaths and more than 200,000 hospitalizations in the U.S. every year. It causes illness in about 10% to 20% of the general population annually, resulting in substantial losses in work, productivity, and an estimated $3 to $15 billion in health care costs.
Rates of infection are highest among children five to 14 years of age, but rates of serious illness and death are highest among children younger than two years of age, persons 65 years of age and older, and persons of any age with medical conditions, such as cardiovascular and pulmonary diseases. People in these groups and with these illnesses are at an increased risk of complications.
Although complete protection might not be provided to all susceptible individuals, the single most effective method of preventing influenza, its complications, and death is immunoprophylaxis with vaccination. Each year, global surveillance of influenza aids in the identification of antigenic variations, allowing for annual standardization of the influenza vaccines. The vaccines are also formulated to consist of two types of influenza A strains and one type of influenza B strain, according to U.S. Public Health Service (USPHS) recommendations and requirements.
Table 1 Influenza Vaccines Currently Available in the U.S.
|FluMist LAIV*||MedImmune Vaccines||Single-dose nasal inhaler||Healthy,nonpregnant persons 5 to 49 years of age|
|Fluzone TIVj||Sanofi Pasteur||Multidose vial
Single-dose prefilled 0.5-ml syringe or vial Single-dose prefilled 0.25-ml syringe
|>6 months >36 months 6 to 35 months|
|Fluvirin TIV||Chiron Corporation||Multidose vial
Single-dose prefilled 0.5-ml syringe
|>4 years >4 years|
|Fluarix TIV||GlaxoSmithKline||Single-dose prefilled 0.5-ml syringe||>18 years|
|* LAIV = live, attenuated influenza vaccine. f TIV = trivalent inactivated influenza vaccine.|
To receive optimal protection from influenza infection during the peak months of December through March, individuals should receive vaccinations during October and November.
Currently, two types of vaccine are available in the U.S. (Table 1):
- live, attenuated influenza vaccine: FluMist (Medlmmune/Wyeth)
- trivalent, inactivated influenza vaccine: Fluzone (Sanofi Pasteur); Fluvirin (Chiron); and Fluarix (GlaxoSmithKline).
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Fluarix is an intramuscularly administered vaccine, indicated for patients 18 years of age or older against influenza virus types A and B, which are contained in the vaccine. It is the newest of the trivalent, inactivated, split-virion influenza vaccines. Fluarix was approved on August 31, 2005, and became available for use during the 2005-2006 influenza season.