Duke Medicine: Multiple vaccines and autism

Do multiple vaccines somehow overwhelm a child's immune system? Could they be a cause of autism?

Dr. Jeffrey P. Baker, director of Duke's History of Medicine Program and an associate clinical professor of pediatrics, takes a look.

This was the question at the heart of the Federal Vaccine Court’s decision to award damages to Hannah Poling, a girl with a mitochondrial disease (a very uncommon disorder disrupting her ability to process nutrients) who regressed developmentally and developed signs of autism after receiving several vaccines at age 19 months.

Cases such as Hannah’s are tragic, but raise more questions than they answer. There are in fact rare children with silent metabolic disorders who may develop normally until suddenly regressing after the stress of a childhood infection. Whether vaccines are a risk has not been proven. Certainly, the infections that vaccines prevent do constitute a danger for these children. Even if we could identify at-risk children, it is far from clear that holding or splitting vaccines would do them a service.

Before accepting the “multiple vaccine” hypothesis, it is worth remembering that more vaccines does not mean more stress on the immune system. The 14 vaccines given to young children expose them to a total of about 150 immunological units, or antigens. The MMR, for all the ballyhoo, contains only 24. In contrast, the old smallpox vaccine included 200 proteins, and the whole cell pertussis vaccine used before the 1990s contained 3,000.

In a nutshell, while more vaccines are being given to infants, these vaccines are far more targeted and purified than was the case twenty years ago. This is why giving vaccines separately makes so little sense to the scientific community. Splitting vaccines certainly makes the schedule even more complicated, and will likely lead to lower immunization rates. When these rates fall below a certain threshold in a community, outbreaks become possible. This has already happened with respect to whooping cough and measles in various locations in the United States.

It will always be possible to think of new mechanisms linking vaccines and autism as others are disproven. But after 10 years of extensive research on vaccines, it is time to entertain other ideas regarding environmental exposures. Vaccine opponents consistently disparage the positive benefits of vaccines, which the vast majority of physicians and public health leaders regard as one of our most powerful tools to protect the health of our children. Deferring or declining vaccines has consequences for our neighbors’ children as well as our own. It is important to learn about the diseases they prevent prior to questioning their benefits.