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Influenza (cont.)

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How effective is the flu vaccine?

Vaccine efficacy also varies from one person to another. Past studies of healthy young adults have shown influenza vaccine to be 70%-90% effective in preventing illness. In the elderly and those with certain chronic medical conditions such as HIV, the vaccine is often less effective in preventing illness. Studies show the vaccine reduces hospitalization by about 70% and death by about 85% among the elderly who are not in nursing homes. Among nursing-home residents, vaccine can reduce the risk of hospitalization by about 50%, the risk of pneumonia by about 60%, and the risk of death by 75%-80%. However, these figures did not apply to the 2014-2015 flu vaccine because the quadrivalent (four antigenic types) vaccine did not match well with 2014-2015 circulating strains of the flu (vaccine effectiveness was estimated to be 23%). This occurs because the vaccine needs to be produced months before the flu season begins, so the vaccine is designed by projecting and choosing the most likely viral strains to include in the vaccine. If drift results in changing the circulating virus from the strains used in the vaccine, efficacy may be reduced. However, the vaccine is still likely to lessen the severity of the illness and to prevent complications and death, according to the CDC.

Why should the flu (influenza) vaccine be taken every year?

Although only a few different influenza virus strains circulate at any given time, people may continue to become ill with the flu throughout their lives. The reason for this continuing susceptibility is that influenza viruses are continually mutating, through the mechanisms of antigenic shift and drift described above. Each year, the vaccine is updated to include the most current influenza virus strains that are infecting people worldwide. The fact that influenza viral genes continually change is one of the reasons vaccine must be taken every year. Another reason is that antibody produced by the host in response to the vaccine declines over time, and antibody levels are often low one year after vaccination so even if the same vaccine is used, it can act as a booster shot to raise immunity.

Many people still refuse to get flu shots because of misunderstandings, fear, "because I never get any shots," or simply a belief that if they get the flu, they will do well. These are only some of the reasons -- there are many more. The U.S. and other countries' populations need to be better educated about vaccines; at least they should realize that safe vaccines have been around for many years (measles, mumps, chickenpox, and even a vaccine for cholera), and as adults they often have to get a vaccine-like shot to test for tuberculosis exposure or to protect themselves from tetanus. The flu vaccines are as safe as these vaccines and shots that are widely accepted by the public. Consequently, better efforts need to be made to make yearly flu vaccines as widely acceptable as other vaccines. Susceptible people need to understand that the vaccines afford them a significant chance to reduce or prevent this potentially debilitating disease, hospitalization and, in a few, a lethal flu-caused disease.

Medically Reviewed by a Doctor on 9/29/2017

Source: MedicineNet.com
https://www.medicinenet.com/influenza/article.htm

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