July 28, 2016
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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.

Recent studies suggest that in younger children (ages 2-8) the nasal spray flu vaccine may prevent about 50% more cases of flu than the vaccine administered by the flu shot. Therefore, children in this age group who have no contraindications should receive this form of the vaccine if it is available. However, the CDC recommends that vaccination not be delayed if this form is not available; the flu shot should be given in this case.

Medically Reviewed by a Doctor on 4/28/2016

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

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