Immunization Schedule, Adults (cont.)
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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.
Mai Kim Lai, MD
Douglas C Finefrock, DO
Gregory L Walker, MD, FACEP, Ped EM
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