Why flu vaccine is rarely effective

By | April 21, 2008

Why flu vaccine is rarely effective

If you got flu shot and still came down with the flu symptoms like fever, cough and running nose, you should not be alone. A study released last week by the Centers for Disease Control and Prevention said the effectiveness of this year’s vaccine was estimated at only 44 percent, The New York Times reported.

What’s gone wrong with the vaccine then?  According to the times, what makes it so hard for a vaccine to effectively prevent the flu is that the virus changes from year to year and experts would have to GUESS what forms of virus will be circulating for the next flu season based on the current year.  Based on the guesstimation, experts formulate a vaccine to protect against those targeted strains.

The newspaper goes on to explain usually the experts’ guess work is pretty good and make the vaccine’s efficacy at 70 to 90 percent in healthy adults. But this year they guessed it wrong and made many recipients miserable.

This year’s vaccine was designed to protect against two strains of influenza A and one strain of influenza B.   This is probably true for the vaccines made for previous years, according to some source.  Based on data collected from central Wisconsin, the vaccine was said to be 58 percent effective against the predominant strain of influenza A, but ineffective against the B strain.

East and Southeast Asia have been blamed as the original sources of flu viruses. The times reported that an international team led by Britain researchers claimed based molecular and genetic analysis that they have figured out how seasonal flu strains evolve and sweep around the world.

According to the theory proposed by the researchers, new flu strains emerge in several countries in East and Southeast Asia and spread through travelers to Europe and North America after as short as six to nine months, and then continue their journey until they reach South America where they die out.

Although the sources of viruses could provide some opportunities for researchers to study the strains of flu viruses so that a potentially effective flu vaccine may be possibly made for the next flu season, the story reported by the times does not explain in sufficient detail why the vaccine is so ineffective.

The official explanation by the CDC may be only part of the story.  In an article published in 2004 by the Center for Medical Consumers, which is a not-for-profit organization that does not accept any funding from the drug industry, Maryann Napoli, the staff writer for the Center, explains why flu vaccine is rarely effective.

It is commonly known that flu viruses change from year to year and researchers have to do some guesswork to make a choice as to how to construct the flu vaccine for the next season.  The choice is based, according to Napoli, on a combination of guesswork, flu outbreaks in Asia, and the recommendations of the world Health Organization.

But what is not as commonly known is that the vaccine is more likely to be effective against the type that causes fewer than 15 percent of all flu cases.  This is the one caused by influenza A or B.  And researchers refer to all other forms of flu as influenza-like illness.  But both types, influenza or influenza-like produce exactly the same symptoms – headache, fever, muscle aches, cough and runny nose.  That probably explains why the official estimate on the vaccine efficacy is always higher than 15 percent.

Vaccine researcher Tom Jefferson, MD, was quoted in Napoli’s article as saying “The flu is not caused by a single ‘bug’-about one-third of all influenza is caused by an unknown agent; about one-third are caused by rhinoviruses, the same viruses that cause the common cold; and the remainder are a mixed bag of other agents including influenza A and B viruses and members of the coronavirus family.”

The difficulty with making an effective flu vaccine is that they all appear to the same illness and one cannot forecast how much of the influenza viruses in the upcoming flu season will be influenza A or B, according to Dr. Jefferson who was cited as saying “yet the public is never told this.”

In an editorial published in the British Medical Journal, Dr. Jefferson said vaccination successes are largely confined to influenza A and B, the type that accounts only for a small percentage of all influenza cases.

Flu vaccine has proved to be a controversial issue.  Critics said that the recommendation for the vaccine is not justified based on both the severity of the flu and the efficacy of the vaccine.  Official reports project that deaths from the flu can be as many as 36,000 a year.  But critics said that the death toll includes both deaths from the flu and pneumonia. The actual number of death for any given year may not exceed 300. – foodconsumer

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