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Flu Basics

Author(s): Sonia Rahmati Clayton, PhD, and Nancy Moreno, PhD

Flu: Prevention

The influenza vaccine is the single best preventative measure. Currently there are two types of vaccines available. The "flu shot" contains an inactivated virus and usually is administered to people older than 6 months. About 55 million flu shots will be available in the United States this season. The second vaccine is a nasal spray made with live but weakened flu viruses. This vaccine is approved for healthy people aged 5 to 49, not including pregnant woman. Vaccinations are not recommended for individuals who are allergic to chicken eggs, have had a severe reaction to an influenza vaccination in the past, have developed Guillain-Barre syndrome within six weeks of a previous vaccination, are less than six months of age, or have a fever.

Because of a shortfall in flu vaccine production this season, the Centers for Disease Control and Prevention (CDC) is recommending that certain people be given priority for getting a flu shot. People in the following groups should seek vaccination this season: all children aged 6-23 months; adults aged 65 years and older;   persons aged 2-64 years with underlying chronic medical conditions; all women who will be pregnant during the influenza season;  residents of nursing homes and long-term care facilities; children aged 6 months-18 years on chronic aspirin therapy; health-care workers involved in direct patient care; and  out-of-home caregivers and household contacts of children aged <6 months. These are people who are at high risk for serious flu complications or are in contact with people at high risk for serious flu complications.

The CDC requests that people who are not included in one of the priority groups forego or defer vaccination because of the vaccine supply situation. This means that preventive measures-covering one's mouth when coughing or sneezing, staying home if infected with flu, avoiding touching of the mouth and nose, and washing hands frequently-will be even more important this flu season.

Due to genetic changes in the virus, flu vaccines are adjusted each year. Changes are based on international surveillance of the virus and scientists' predictions about which types viruses will be circulating during the coming year. The vaccination begins to take effect about two weeks after administration, because it takes the body this long to develop antibodies against the influenza virus.