May 19, 2004
Although numerous studies have found no link between autism and vaccines, many parents have still opted not to have their children immunized, putting them at great risk of contracting deadly diseases. But a new groundbreaking report from the Institute of Medicine (IOM) reaffirms that childhood vaccines, as well as a mercury-containing preservative called thimerosal found in some vaccines, do not cause autism.
The measles-mumps-rubella (MMR) vaccine, especially, has come under fire over the years, despite many scientific reports indicating that there's no clear evidence linking the vaccine to autism. This latest report from the IOM comes 2 months after a long-disputed 1998 study was retracted suggesting a possible link between autism and the MMR vaccine. Even before the 1998 study was retracted, it was rejected by all major health organizations - including the American Academy of Pediatrics (AAP), the National Institutes of Health (NIH), the Centers for Disease Control and Prevention (CDC), and the World Health Organization (WHO). In addition, two prior IOM studies found no link between autism and vaccines. Still, some parents continued to be fearful of the MMR vaccination.
In an effort to reduce child exposure to mercury and other heavy metals, thimerosal - an organic mercury compound - began being removed from kids' vaccines in 1999. Now, vaccines for infants and young children contain no or very little thimerosal. Nevertheless, there is no reason to believe that thimerosal is linked to autism, according to the latest IOM report, which is the final in a series on vaccine safety sponsored by the CDC and the National Institute of Allergy and Infectious Disease (NIAID).
About Autism
Autism is a developmental disorder that affects as many as one in 500 people in the United States. Usually diagnosed in toddlers, it's characterized by mild to severe impairment of communication and social interaction skills. Although a specific cause of autism has not been found, several theories exist.
Although the number of children diagnosed with autism may be increasing, the rates of MMR vaccination are not. In London, diagnosis of autistic disorders has been on the rise since 1979 but rates of MMR vaccination haven't increased since routine MMR vaccination began in 1988. In addition, the average age of diagnosis of autism has been found to be the same in children who have or who have not received the MMR vaccine. What many researchers are discovering is that subtle symptoms of autism are often present before a child's first birthday - sometimes even in early infancy - but often go unnoticed until the symptoms are more obvious to parents.
So what could explain the increased rates of autism in recent years? For one thing, a broader definition of autism that can be applied to more children who show varying degrees of symptoms. There's also been a greater awareness of the condition among health professionals, which has lead to more diagnoses.
As for what causes the condition, medical experts believe it may be a combination of factors. A genetic basis is suspected, evidenced by the fact that the identical twin of a child with an autistic disorder will have a 92% chance of having one, too, while a fraternal twin has only a 10% chance. Research also points to the possibility that other factors, such as toxins or viral infections, may cause or trigger autism before birth. Medical researchers all over the world continue to investigate the possible causes of autism.
About Immunizations
One of the best means of protecting your child against contagious diseases, immunization (vaccination) is an artificial way of creating immunity to certain diseases. Vaccines work by preparing your child's body to fight off specific infectious illnesses. Each immunization (given through a shot your child receives) contains either a dead or a weakened germ (or parts of it) that causes a particular disease. Following vaccination, your child's body develops protection against the disease by making antibodies that recognize specific parts of that germ. This permanent or long-standing response means that if your child is ever exposed to the actual disease, the antibodies are already in place and ready to combat the germ, so your child doesn't get sick. This is called immunity.
Vaccines are one of the most effective weapons we have against disease. Although reactions to vaccines occur in some cases, they are rarely serious - and the health benefits of vaccination clearly outweigh the risks for almost all children. Immunizations can protect your child against several potentially serious illnesses (particularly when more and more people use them) and give these diseases fewer chances to take hold in a population. Getting your child vaccinated is one of the most important things you can do to ensure his or her health throughout childhood and into adulthood.
Reviewed by: Steven Dowshen, MD
Date reviewed: May 2004
