Scientific Evidence Does Not Support Flu Shot Recommendations
The benefits of influenza vaccines are exaggerated and little is known about their safety, according to a new report in the British Medical Journal.
Drawing from studies conducted over a 30-year period, Tom Jefferson, MD, concludes that the scientific evidence supporting the annual flu vaccine is of poor quality, yet many governments, particularly those of the U.S. and Canada, have a policy that urges large segments of the population,even including babies from 6 to 23 months, to be vaccinated yearly.
“There is a large gap between policy and evidence,” says Dr. Jefferson, who works with the Cochrane Collaboration, an independent, international organization that evaluates clinical trials involving medical interventions, such as vaccines, in order to determine their effectiveness.
His new report entitled “The Prevention of Seasonal Influenza — Policy Versus Evidence” is based on his assessment of all the evidence that might support claims made for influenza vaccination, including reduction in the number of people who get influenza and the rate of sick days, hospitalizations, and deaths in the elderly.
“At best, the effect of the influenza vaccine is slight,” said Dr. Jefferson in an interview, referring to its benefit to healthy adults and children as well as those with chronic conditions like asthma.
Both influenza and influenza-like illness have exactly the same symptoms — headache, fever, muscle aches, cough, runny nose — but the vaccines are aimed at only influenza A or B, which researchers call real influenza. “Influenza A or B represents less than 10% of all influenza-like illness,” explained Dr. Jefferson. “The rest are caused by anywhere from 152 to 200 viruses. The common cold, for example, is an influenza-like illness.
“Because there is no way of telling the difference between influenza and influenza-like illness on the spot, vaccine performance can only be realistically judged in formal studies carried out during the [influenza] season and usually published several months or years later. Given all these very complicated permutations [different variations], the best way to judge how well inactivated influenza vaccines [the most commonly used vaccines which contain killed viruses] perform is to synthesize all data from known studies into what is called systematic reviews.”
The new report by Dr. Jefferson found that the systematic reviews show a consistent pattern of modest or no effect” of inactivated vaccines. What’s more, the original studies were of poor quality, especially those that have not randomly assigned half of the participants to receive a placebo vaccine. (A “placebo” is a substance of no medical value.)
Two years ago, for example, Dr. Jefferson co-authored a review of all trials that looked at influenza vaccines given to children under age two and found they were no better than a placebo.