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Immunization Schedule, Adults (cont.)


Influenza is commonly called the flu and is caused by a virus. The illness usually goes away by itself without complications, but elderly people or those with serious illnesses may be less able to fight off the disease, resulting in complications. A rare complication known as Reye syndrome can occur with influenza and other viral diseases. It consists of rapid liver failure and brain function abnormalities and can cause death. It is more common in children and is associated with the use of aspirin during these viral infections. This is the reason why doctors warn parents not to give children aspirin for any illness.

Widespread cases of flu (called pandemics) can occur when new strains appear in a population that lacks immunity. According to the CDC, the 1957 and 1968 pandemics caused one-fourth or more of the U.S. population to be infected in a period of two to three months.

There are two major types of influenza viruses, called A and B. Influenza A viruses tend to change over time and become more resistant to the vaccine developed the previous season. Influenza B viruses exhibit fewer changes. Therefore, the development of a flu vaccine is based on the commonest strains of the year before. A new vaccine must be developed each year. To be protected against the most likely strains of virus in an upcoming flu season, a new shot must be taken each year.

Although they are not substitutes for the vaccine, antiviral medicines such as zanamivir (Relenza) and oseltamivir (Tamiflu) can reduce the symptoms or prevent influenza A. These drugs can decrease the chance of infection in someone exposed to influenza A if they have not already been vaccinated. The medicine must be started immediately after exposure and continued for 10 days. During an outbreak, a recently vaccinated person may also need to take these medications while allowing time for the immunity to develop from the shot. Other antiviral drugs, such as amantadine (Symmetrel) and rimantadine (Flumadine), have been previously recommended. As of January 2006, the Centers for Disease Control and Prevention (CDC) no longer recommend amantadine and rimantadine due to the development of resistance of these antivirals for influenza prophylaxis. For more information, see Recalls and Alerts, Jan. 17, 2006.

  • Who gets the vaccine: The flu vaccine is recommended yearly for all adults. All adults 50 years or older; anyone 6 months to 50 years of age with chronic diseases (such as heart, lung, kidney, diabetes, asthma, or blood diseases); anyone living in chronic care facilities, such as nursing homes; those 6 months of age or older living with at-risk individuals; children 6 months to 5 years of age (because of the high risk of hospitalization); pregnant women beyond the third month of pregnancy during influenza season; health-care workers exposed to at-risk individuals; travelers to countries where there are influenza activities; and anyone who would like to reduce the chances of becoming ill should get a flu vaccine.
  • When given: anytime during influenza season (November through March). October through November is the best time, offering highest protection. Individuals at higher risk should receive their flu vaccine as early as possible. Children younger than 9 years receive two doses (one month apart) if they have not previously received influenza vaccine.
  • Side effects: soreness at injection site for one to two days. Some people have a reaction to the virus protein in the vaccine that causes flulike symptoms such as mild fatigue and muscle aches. They occur six to 12 hours after vaccination and last up to two days. Some people have an allergic reaction to egg protein used in the vaccine. Some people may have an anaphylactic reaction to the vaccine or to eggs and should not have the shot. Pregnant and breastfeeding women may take the vaccine.
  • Influenza vaccine is also available as a nasal spray (FluMist) for healthy children 5 years of age or older, adolescents, and adults 49 years of age or younger.
Medically Reviewed by a Doctor on 7/20/2016

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