Influenza epidemics occur yearly in the United States, usually between late December and February.  These epidemics can be deadly, resulting in 20,000 to 40,000 excess fatalities in the United States each "flu season".  Most of these deaths occur as a result of complications of underlying chronic diseases (heart and lung) or from secondary bacterial infections which take advantage of an influenza-infected persons weakened condition.  While careful handwashing and other infection control precautions are very important, the only highly effective way to avoid influenza infection is to teach your immune system how to defend itself before the virus invades your system.  Influenza vaccination ("flu shots") is a safe and effective way to help your immune system develop a preventive immunity to this infection.  Due to the constantly changing nature of the influenza virus, this immunity must be updated each year to assure you will be protected from the types of influenza that are likely to spread that year.

Groups of people who are at high risk of complications from influenza infection include:

• persons aged >65 years; 
• residents of nursing homes and other chronic-care facilities that house persons of any age who have chronic medical conditions;
• adults and children who have chronic disorders of the pulmonary or cardiovascular systems, including asthma; 
• adults and children who have required regular medical follow-up or hospitalization during the preceding year because of chronic metabolic diseases (including diabetes mellitus), renal dysfunction, hemoglobinopathies, or immunosuppression (including immunosuppression caused by medications or by human immunodeficiency [HIV] virus); 
• children and adolescents (aged 6 months--18 years) who are receiving long-term aspirin therapy and, therefore, might be at risk for developing Reye syndrome after influenza infection; and 
• women who will be in the second or third trimester of pregnancy during the influenza season.

Other priority groups for influenza vaccination are:

• persons between 50 and 64 years of age
• physicians, nurses, and other personnel in both hospital and outpatient-care settings, including medical emergency response workers (e.g., paramedics and emergency medical technicians); 
• employees of nursing homes and chronic-care facilities who have contact with patients or residents; 
• employees of assisted living and other residences for persons in groups at high risk; 
• persons who provide home care to persons in groups at high risk; and 
• household members (including children) of persons in groups at high risk.
• healthy children ages 6-23 months

This final recommendation concerning healthy children is new for 2002 and has caused some confusion among parents and health care providers.  The medical basis of the recommendations is that infants and toddlers are at increased risk of complications from influenza leading to hospitalization.  Influenza vaccination is effective in infants as young as 6 months of age.  After children reach 2 years of age, their risk of complications from influenza diminishes.  Many childhood vaccines  are provided by state and federal funding sources and parents (or their health insurance) need only pay for the cost of administering the vaccine.  Unfortunately, influenza vaccination for healthy infants and toddlers is not covered by these programs and parents are liable for the full cost of the vaccine.  State and federal influenza vaccine is available for children aged 6 months to 18 years of age who are in the "high risk for complications" group, i.e. those who have chronic health conditions (including asthma).

Although it is especially important for the people listed in the high risk groups to have annual influenza vaccination, this immunization is also a good idea for anyone who wants to reduce their chance of acquiring a nasty respiratory infection that can last up to 2 weeks.  Unlike the past two flu seasons, there is no shortage of influenza vaccine this year.