Vaccination and Autism—Data Rejects Link By Lisa Glickstein, Ph.D, Triplet Mom Originally printed in May, 2006 Vaccination has changed the course of human history in the last 100 years. Influenza, polio, measles, mumps, and rubella (German measles) that used to kill or cripple scores of children and adults each year are generally thought of as a historical footnote. However, the last 15 years has seen two intersecting trends – resurgence of infectious diseases (including those for which there is no vaccine, such as tuberculosis and HIV/AIDS) and a growing skepticism of vaccines. Beginning perhaps with safety concerns about the pertussis (then called DPT) vaccine, this has been followed by withdrawal of the rotavirus vaccine due to an increased risk of a fatal intestinal complication, withdrawal of the Lyme disease vaccine due to consumer fears over a never-proven link to Lyme arthritis, and plummeting vaccination rates in children. Unfortunately, this has led to outbreaks of measles and mumps, and new legislation banning the preservative thimerosal in vaccines over the objection of 22 medical organizations. How does vaccination work? Vaccination works to prevent disease in individuals, and to decrease disease incidence in groups. A killed or inactivated virus or bacteria, or a small building block from the same, is injected into the person along with a fluid that contains preservative, and a substance called an adjuvant (usually aluminum) to help activate immune cells. The person’s immune system recognizes the material as foreign and generates an immune response with antibody production that is specific for that germ. Our immune systems respond faster and more intensely to a second exposure to a bacteria or virus, so if the person later is infected by that germ they should make an enhanced immune response, eradicate the organism, and not get sick. There is a lot of variation in immune response, and so a vaccine may not work in every single individual that gets vaccinated. Luckily, many viruses or bacteria rely on being transmitted from one sick person to the next in order to spread. If enough people are successfully vaccinated and do not get sick, they protect the few people who were not vaccinated or in whom the vaccine didn’t generate enough immunity. When vaccine rates fall, outbreaks start to occur. What is thimerosal? Thimerosal is a preservative that contains the metal, mercury. Mercury is toxic at high doses to nerve cells. It is used in some, but not all vaccines (as well as some contact lens solutions and other biological solutions). What is neurodegenerative disorder? Neurodegenerative disorder is another term for the group of related syndromes that includes autism. As this group includes both milder and more severe forms, it is also sometimes termed autism spectrum disorders. Another frequently used term is pervasive developmental delay (PDD). These all refer to the group of disorders usually characterized by some combination of social and language delays in children who frequently have normal or even high intelligence. The onset can be gradual, or appear as a sudden loss of previous language or social behaviors. It is very likely that PDD or autism spectrum encompasses a range of unique causes that lead to similar outcomes by affecting the same part of the brain. This can greatly complicate large studies of incidence. Autism diagnosis has increased over the years due to greater recognition of the milder (or higher-functioning) forms of the disease, and better understanding of the physical rather than psychological basis of the illness. However, the incidence of autism also appears to be increasing slightly overall, although this has been difficult to prove because diagnosis has changed so much even over the past 20 years. What are the National Academy of Sciences and the Institute of Medicine? The National Academy is a group of scientists that are honored with election based on their career research accomplishments, including specific findings (similar to the Nobel Prize) and publication records. They include the best and brightest scientists and doctors in the country. Along with the honor of election comes a responsibility to report to the President of the United States and the Congress about scientific issues of importance to the nation. In this capacity, the National Academy commissions reports on specific topics, prepared by committees of chosen members, that are published by the National Academies Press, and available for free online (or for a fee as bound books) to anyone in the country. The President or Congress can also request a study or report on a particular topic to be prepared. The Institute of Medicine is a subgroup of the National Academy that specifically takes on issues of medical conditions. They have prepared a number of reports examining the evidence for a link between vaccines and autism, or thimerosal and autism, over the past 10 years. Their most recent report was published in 2004. How was that study conducted? The committee from the Institute read and discussed all of the published research from the US and abroad concerning the link between vaccines, thimerosal, and autism. There were many types of studies, including animal or cell culture studies on the effects of thimerosal and vaccination on the brain, to large population studies on the rates of autism in children who received thimerosal-containing, or thimerosal-free vaccines. The members discussed how each study was conducted, how did the authors define autism, how did they measure outcomes, were the statistical tests used appropriate, and could they be compared to other studies. The published report, which is 215 pages long, reports their discussion of each study, and their findings after considering all of the studies together. It also contains recommendations for public health policy and future research. What were the findings? The Institute found that the current research did not support a link between vaccination (specifically, MMR vaccine) and autism, nor between thimerosal and autism. Specifically, there was only one group of studies that claimed to show that a link between thimerosal and autism exists; the same two authors wrote all, and the committee concluded that those studies had a number of very significant flaws that argued against their conclusions being valid. Dr. Mark Geier and his son, David, carried out these studies. Both have served as expert witnesses in many cases against vaccine manufacturers in the United States, and in most of those cases their testimony was ultimately thrown out on appeal. Their names appear on many of the websites warning parents against vaccination, and against thimerosal. The Institute report also noted that an observational study reporting a link between MMR vaccination, intestinal symptoms, and autism, did not have enough patients to prove such a link was not random chance. A letter from 10 of the 13 original authors supported this. Furthermore, after reviewing all of the data, the Institute concluded that future research on autism should be directed at the underlying neurological mechanisms, not on the discredited link to vaccination. Finally, the Institute report noted that because thimerosal has been removed from many childhood vaccines, the total dose of mercury a child would receive with a full course of vaccination is now well below the recommended maximum dose. Therefore, they concur with the recommendation for vaccinating pregnant women and children under 6 against influenza, even though that vaccine still contains thimerosal.