Monday, December 26, 2011

Relative risk vs Absolute risk

A new study in The Lancet Infectious Diseases reveals that the flu vaccine prevents lab confirmed type A or type B influenza in only 1.5 out of every 100 vaccinated adults(98.5% Useless) … but the media is reporting this to mean "60 percent effective." Some clinical trials are only able to show a meaningful benefit because they focus on relative risk reduction rather than absolute risk reduction. In plain English, here's what that means: let's say you have a study of 200 women, half of whom take a drug and half take a placebo, to examine the effect on breast cancer risk. After five years, two women in the drug group develop breast cancer, compared to four who took the placebo. This data could lead to either of the following headlines, and both would be correct:
"New Miracle Drug Cuts Breast Cancer Risk by 50%!"
"New Drug Results in 2% Drop in Breast Cancer Risk!"
An important feature of relative risk is that it tells you nothing about the actual risk.

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