The MMR Vaccine and Autism
The current concern about the MMR vaccine and its association with autism is based on three things. The first was an observation that the number of children diagnosed with autism increased dramatically right around the same time the MMR combination vaccine was introduced in the United States and Great Britain. The second was based on a study by Dr. Andrew Wakefield in 1998 published in the respected scientific journal Lancet. The third is based on the fact that children with autism were first diagnosed with the condition right after they received the MMR vaccine.
To look at the first link, it is obvious that the number of children diagnosed with autism increased dramatically around the same time the MMR vaccine was given to many children. The MMR combination vaccine first became available in 1971. Back in the 1970s, 1 in 10,000 children was diagnosed with autism. Currently, it is estimated that 1 in 150 children is expected to have the diagnosis. The timing of the two events could not have correlated better. Many parents looked at this perfect timing and concluded that the MMR vaccine must be responsible for triggering the current global epidemic of autism in developed countries.
However, there are some problems with this association because the way autism was diagnosed changed after the MMR vaccine was introduced, leading to more children being diagnosed as autistic. Prior to the early 1990s, autism had a more narrow definition. The definition of autism changed twice between 1987 and 1994 in the Diagnostic and Statistical Manual of Mental Disorders (DSM). The DSM-III-R and DSM-IV (third edition, revised, and fourth edition, respectively) gave a much more precise definition of autism, thereby allowing clinicians to make a more accurate diagnosis of autism instead of classifying some of these children as mentally retarded as was done in the past. Consequently, more autistic children are being diagnosed correctly today than ever before.
In addition, autism was not a well-known condition prior to the 1980s. Most doctors were not familiar with this condition and therefore could not correctly identify children with autism before that time. Another event that resulted from this increased public awareness was the increasing availability of public services, both in school and in the community, for these children. Consequently, more children are getting diagnosed earlier and correctly so they can qualify for these special assistant programs. Even though the rise of autism occurred around the same time as the MMR vaccine was first introduced to the public, it is unclear that one event led to the other.
The second link between the MMR vaccine and autism was established by the famous study done by Dr. Wakefield published in Lancet. Dr. Wakefield is a Canadian surgeon who studied twelve children in 1998 who purportedly became developmentally delayed after receiving the MMR vaccine. His hypothesis is that the MMR vaccine can trigger inflammation in the intestine, and this inflammation can subsequently allow harmful proteins to enter the bloodstream and the brain. He theorized that autism is the effect of these harmful proteins on the brain. He was the original doctor who proposed that the MMR vaccine should be separated into individual vaccines to prevent intestinal inflammation, even though there is no evidence that separating the vaccines makes any difference to the immune system.
Dr. Andrew Wakefield is currently under legal indictment by the British General Medical Council for professional misconduct. Prior to making the statement that endorses separating the MMR vaccine into individual vaccines, he filed a patent for an individualized measles vaccine, which means he could reap financial gains from widespread use of this single measles vaccine.
To prove his theory, in 2002 he took biopsies from a group of autistic children's intestines and demonstrated the presence of measles virus in the intestinal cells. He found that most autistic children (75 out of 91) have measles virus in the intestinal tissue and that most nonautistic children (65 out of 70) do not have the measles virus in their intestines. This result certainly sounds convincing that the measles virus could somehow be related to autism.
The question is whether the measles virus found in these autistic children's intestines came from the vaccines or from natural measles infection. At the time of the study, measles outbreaks still occurred fairly frequently in Britain, where the study took place. Even though Dr. Wakefield could determine whether the measles virus found in autistic children's intestines was the weakened version from the vaccine or the regular kind from natural infection, he chose not to do so. In addition, recent investigation revealed that Dr. Wakefield had fabricated experimental data in order to support his hypothesis. Most of the coauthors of Dr. Wakefield's published research have since withdrawn their names and support from the report in Lancet.
Ten of the twelve authors of Dr. Wakefield's research later retracted their original conclusion that the MMR vaccine could be implicated in causing autism. The retraction states that no causal link was established between the MMR vaccine and autism.
On the other hand, Japanese scientists (led by Dr. Hideo Honda) had demonstrated in 2005 that children continued to develop autism even when the MMR vaccine was no longer given to an entire group of children. Due to a concern about a possible side effect of the mumps vaccine, the MMR vaccine was no longer recommend for children in the city of Yokohama (population 300,000) from 1988 to 1996. Starting in 1993, not a single shot of the MMR vaccine was given in the entire city. Despite the fact that the MMR vaccination had completely stopped, the number of autistic children continued to rise in the city. In fact, the number of new diagnoses since 1993 nearly doubled compared to the time period before the MMR vaccine was stopped. This clearly demonstrates that children continue to become autistic at an alarming rate even if they have never received the MMR vaccine.
Finally, there is an obvious reason why autism is almost always diagnosed after the MMR vaccine is administered. In order to diagnose autism, speech and social interaction with other children are key diagnostic criteria. Even normal, nonautistic children typically do not have fluent speech before they turn one. In addition, social interactions of infants are typically limited. Autistic children only stand out when the language skills of their nonautistic peers really start to take off. This developmental milestone occurs right around the time when the first MMR vaccine is given.
One convincing fact that makes this temporal relationship unlikely to be a causal one is that autism can sometimes be diagnosed by experienced experts when these children are only six months old. This is far before these children receive their first MMR vaccine. By the time these children who are identified early receive their first MMR shot, they are already autistic. The timing explanation does not work if children were autistic without ever receiving the MMR vaccine.
To this day, scientists do not know exactly which factors can trigger autism. It is clear that it is a strongly genetic condition. It is also clear that autism could be diagnosed before the age of one and before receiving the first MMR vaccine. Finally, even when one entire community stopped administering the MMR vaccine, many children continued to become autistic. These observations make it hard to conclude that the MMR vaccine is solely responsible for the current autism epidemic around the world.