Flu Vaccine

Tuesday, December 13, 2005

The flu vaccine is recommended for persons at risk for influenza-related complications, including: persons 50 years of age or older, residents of LTCF, adults and children who have chronic lung or heart conditions, including children with asthma, adults and children who have required regular medical care during the previous year because of chronic diseases such as diabetes, kidney problems, or problems of the immune system, children and teenagers age 6 months to 18 years who are receiving long-term aspirin therapy and therefore might be at risk for Reye syndrome, women who will be in the second or third trimester of pregnancy during the influenza season, persons who might transmit influenza to high risk individuals such as health care workers, workers at chronic health care facilities, providers of home care, and household members of persons in high risk groups. Because the vaccine is prepared from viruses grown in eggs, patients with serious allergy to egg products should consult with their doctor before receiving the vaccine.

Because the influenza virus changes (or "mutates") slightly from year to year, a new vaccine must be produced and administered prior to each flu season. Each year's vaccine is based on the previous year's flu virus and virus strains known to be circulating in other parts of the world. The vaccine's effectiveness for the current year's flu, therefore, depends upon how well scientists are able to predict which strains will cause infection in a given year.

Patients receiving vaccine make antibodies (proteins) which destroy the virus after the person is exposed; it generally takes about two weeks for the body to make these antibodies. If the circulating virus and strains used for the vaccine match closely, the vaccine may protect 50 to 80 percent of those receiving the vaccine from getting the flu.

Because the influenza vaccine does not contain live virus, it can be administered safely to people with weakened immune systems and does not appear to exacerbate chronic neurologic diseases such as multiple sclerosis. In previous years, a slightly increased risk of Guillain-Barre syndrome (a neurologic disease), was associated with the flu vaccine. Because of this, the vaccine is generally not given to individuals who developed Guillain-Barre syndrome within six weeks after a previous influenza immunization.

The more recent vaccines have been generally well tolerated and reactions have been seen in fewer than 5 percent of cases. Side effects usually consist of low grade fever and mild "flu-like" symptoms for 8 to 24 hours after immunization. Because the vaccine is prepared from viruses grown in eggs, patients with serious allergy to egg products should consult with their doctor before receiving the vaccine.

James Gardner, MD