This year's sudden flu shot shortage may have some health consequences beyond just this year. As this ScienCentral News video reports, researchers have found that alternately getting and skipping flu shots may actually increase your chance of getting sick.
Original Antigenic Sin
On October 5, the Centers for Disease Control (CDC) was notified by the Chiron Corporation that none of its influenza vaccine would be available for distribution in the United States for the 2004– 05 influenza season. This will reduce the expected supply of flu shot available in the U.S. for the 2004– 05 flu season by approximately one half.
Because of this, the CDC is giving the following groups priority for vaccination: all children aged six– 23 months; adults aged 65 years and older; people age two– 64 years with underlying chronic medical conditions; all women who will be pregnant during the influenza season; residents of nursing homes and long-term care facilities; children aged six months– 18 years on chronic aspirin therapy; health-care workers involved in direct patient care; and out-of-home caregivers and household contacts of children aged less than 6 months.
But one bioengineer says that, even if you're not in one of those groups, if you got a flu shot last year, and don't get it this year, you’re at greater risk, too. In fact, you may be worse off than if you'd never gotten a flu shot at all.
image: American Lung Association
Michael W. Deem, professor of bioengineering, physics, and astronomy at Rice University in Houston, Texas, has researched a biological phenomenon known as "original antigenic sin," first discovered in people and farm animals in 1953. Original sin is a theological concept that accounts for human flaws, and an antigen is biologists' term for an invading organism, such as the influenza virus. So original antigenic sin describes an apparent failing in the human immune system—it may recognize a certain strain of a disease, such as the current flu virus strain, but then tries to fight an entirely different strain by "remembering" how it fought the first strain it encountered.
A flu shot gives the immune system something to "remember" to fight off. But the flu virus mutates very rapidly, and the vaccine is changed every year, so skipping that shot one year can mislead the immune system into thinking it knows how to combat the latest strain. "The immune system may use its memory from last year and try to combat this year's flu with last year's antibodies," says Deem. "The memory in the immune system is actually leading the immune system astray." As a result, Deem says, you may be more likely to get the flu during that year, compared to your chances of illness if you had never gotten a flu shot in previous years.
Deem says an annual flu shot keeps the immune system up to speed. "This allows the immune system to build up its repertoire of antibodies that can control the flu for that particular individual," he says. "For rapidly mutating strains such as the flu, the vaccine needs to contain the most likely strains. And it's not simply that all the strains can be included in the vaccine, because the strains interfere with each other to some extent, so there is a limit to how many strains can be put into the vaccine every year."
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