It’s the time of year when everyone is lining up for the annual flu vaccine. Doctor’s offices and employers are holding special clinics, and even many drug stores are offering a poke in the arm to prevent influenza this winter. But do these vaccines actually work?
A systematic review of the literature says they do, a little bit.
The Cochrane Collaboration (one of our favorite resources here at EBL) reviewed 50 reports of the benefits of the influenza vaccine, including 40 randomized-controlled trials involving more than 70,000 people.
Before I explain the results, here’s a little background on the flu: There are more than 200 different viruses that cause influenza with similar symptoms including fever, headache, cough and body aches. It is difficult for vaccine-manufacturers to know which of these viruses will be active in any given year. The World Health Organization does its best to predict what type of flu will be prevalent in a given season, and then recommends which viral strains should be included in vaccinations each year.
Under ideal conditions – meaning that the vaccine completely matches the active flu viruses – 33 healthy adults need to be vaccinated to avoid one person coming down with the flu. But the vaccine rarely matches the active flu viruses entirely. In more realistic conditions where the vaccine partially matches the active flu viruses, 100 people need to be vaccinated to avoid one set of influenza symptoms.
None of the studies showed that vaccines reduced the number of people hospitalized for the flu. Also, studies show the vaccine caused one case of Guillian-Barré syndrome, a neurological condition leading to paralysis, for every one million vaccinations.
The bottom line: The flu vaccine will reduce your chances of getting sick this winter, but provides no guarantees of completely avoiding the flu.
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