About 36,000 Americans die each year from complications of flu. An estimated 10 percent to 20 percent of U.S. residents get the flu each year with an average of 114,000 people hospitalized for flu-related complications. The flu vaccine is specifically recommended for people who are at high risk for developing serious complications resulting from influenza infection.
Studies show when the vaccine matches the actual circulating flu strains for that season, the vaccine is 70 percent to 90 percent effective in preventing illness in healthy young adults. In the elderly and those people with certain chronic medical conditions, the vaccine may be slightly less effective. It has been shown, however, that when people who were vaccinated get the flu, their risk of hospitalization and death from the flu is greatly reduced.
The Centers for Disease Control and Prevention recommend the flu vaccine for the following people:
- People ages 50 or older
- Persons of any age with chronic heart, lung and kidney disease or with diabetes
- Persons who have a suppressed immune system (Examples include people with HIV infection, those who have undergone organ transplantation and people taking medications such as chemotherapy or steroids that alter the immune system’s response to illness.)
- Residents of nursing homes and other chronic-care facilities housing persons of any age with chronic medical conditions
- Children and teenagers who are receiving long-term aspirin therapy and who may therefore be at risk for developing Reye’s syndrome following an influenza infection
- People in close or frequent contact with those persons identified as high risk (Examples include health care workers, nursing home employees and caretakers of individuals who are considered high risk.)
- Other persons who wish to reduce the likelihood of becoming ill with the flu.
In the United States, the flu usually occurs from about November until April. The number of flu cases is normally low until December, and peak flu activity is seen between late December and early March.
The flu vaccine is best administered between September and mid-November since it takes about one to two weeks after vaccination for the body to develop antibody protection against the flu. Adults and older children are vaccinated in the upper arm muscle and young children in the thigh muscle. The benefits of the standard flu vaccine last less than one year, so it is necessary to be revaccinated each year.
Most people report no side effects from the flu vaccine. The most serious side effect that can occur in people receiving the vaccine is an allergic reaction in those who have a serious allergy to eggs, since the viruses used in the vaccine are grown in hens’ eggs. For this reason, people who have an allergy to eggs should not get the flu vaccine. Other reported side effects associated with the flu vaccine include some soreness at the injection site (reported in less than one third of those who get the vaccine) and mild headache or low-grade fever for about a day after getting the vaccine (reported in 5 percent to 10 percent of those who get the vaccine).
Some people do not receive the flu vaccine because they erroneously believe that the vaccine may cause the flu. This is not possible, since the vaccine is manufactured from killed influenza viruses, which are not capable of causing infection.