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Vaccine FAQ
March 6, 2008 -- What are the real benefits -- and the real risks -- of U.S. childhood vaccines? Do vaccines cause autism? Why do some vaccines still contain the controversial, mercury-based compound thimerosal? WebMD went to experts for the answers to some frequently asked questions:
1. What are vaccines?
"Vaccines help our bodies make protection against life-threatening infectious diseases," says Anne Schuchat, MD, director of the CDC's National Center for Immunization and Respiratory Diseases.
When a germ invades the body, the immune system recognizes it as a foreign invader. This sets off a cascade of events. The immune system makes antibodies, which are specialized molecules that stick to the invader and either inactivate it or mark it for destruction. Specialized immune cells also seek out and destroy germs and cells in which germs are multiplying. Other immune cells remember the germ so the next time a germ of the same kind tries to invade the body, the immune system will be able to mount an immediate response.
Vaccines offer a shortcut to immunity by raising protective immune responses before a germ invades. This gives the body a crucial head start that lets it prevent dangerous infections or make them less severe.
2. I heard that the U.S. government says childhood vaccinations might cause autism and something called mitochondrial disease. Is this true?
In March 2008, the Division of Vaccine Injury Compensation (DVIC) at the Department of Health and Human Services agreed there is a possibility that vaccination "aggravated an underlying mitochondrial disorder" in a young girl. The girl suffered "a regressive encephalopathy with features of autism spectrum disorder" after receiving five standard childhood vaccines in July 2000. The DVIC agreed that the girl and her family should be compensated.
Mitochondria are the energy-making structures inside the cells of our bodies. They have their own DNA, which we inherit directly from our mothers. Mitochondrial diseases or disorders are caused by defects in mitochondrial DNA, or by defects in regular DNA that affect mitochondrial function.
People with mitochondrial disease may get too little energy to power the immune system, the nervous system, and/or other important bodily functions. Or their dysfunctional mitochondria allow toxins to build up within cells.
The case settled by the DVIC is a legal case, not a scientific study. The DVIC agreed only that it is biologically plausible for a girl with a mitochondrial disorder to have been injured by her vaccination. The DVIC did not say that vaccines cause autism.
Does vaccination truly aggravate mitochondrial disease? WebMD asked Chuck Mohan, executive director and CEO of the United Mitochondrial Disease Foundation.
"There is no scientific proof that vaccines cause mitochondrial disease or autism, but there is very little scientific research in this area," Mohan says. "Persons with mitochondrial disease don't necessarily have autism, and persons with autism don't necessarily have mitochondrial disease. The tie-in is that in this case, mitochondrial disease was exacerbated by vaccination."
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