Even though no association between autism and any childhood vaccine has ever been scientifically established, many parents hold this firm conviction. Despite statements made by prestigious and trustworthy groups like the American Academy of Pediatrics and the American Medical Association, many parents would rather listen to activist groups and people without any medical credentials. It is even more ironic that most of these parents tend to be more educated than the general public.

Bad Timing

Before embarking on an examination of the relationship between autism and the measles-mumps-rubella (MMR) vaccine, it is first necessary to clarify a basic point of logic. A temporal association (that is, an association in time, when one thing follows another) is not the same as a causal relationship (that is, a cause-and-effect relationship, when one thing causes something else to happen). To explain this further, here's an examination of a phenomenon that is unrelated to vaccination or autism.

We all know that road traffic tends to be heaviest during the morning and evening rush hours, when people are commuting to and from work. It is also true to say that traffic is most congested when the sun is rising and when it is going down. That means we can accurately predict that traffic jams will occur at around the time of sunrise and sunset. Would it be logical to state that the sun therefore has some mysterious influence on the flow of traffic? Or could we say that heavy traffic causes the sun to rise or set? This is obviously not the case. Just because the two events happen at around the same time, it does not follow that there is any temporal association between the two — that is, one does not necessarily trigger the other.

The argument that some scientists initially used to propose the alleged link between the MMR vaccine and autism was based on a similar temporal association. The MMR vaccine is usually administered right after a child turns one year old. Most cases of autism are first diagnosed at around this time. It is not uncommon for parents of autistic children to recall that things first started going wrong immediately after the administration of the MMR vaccine.

Many vaccine opponents argue that autism must be caused by vaccination rather than a genetic component. If autism was an inherited condition — that is, something the child was born with — wouldn't it make sense for some behavioral problems to surface before the age of one? In order for this argument to hold water, children affected by autism should show no signs of the disorder prior to receiving the MMR vaccine. As investigation into the causes of autism has become more sophisticated, it has become clear that this prediction is false.

Child development experts are now able to identify children with autistic traits at an earlier and earlier age. Most autistic children manifest some subtle behavioral abnormalities before they are six months old. Many of the developmental clues are difficult to detect unless they are monitored by a pediatric developmental expert, but they are present nevertheless.

If signs of autism manifest themselves earlier than a year, why are most cases of autism diagnosed after that age? This is because these signs may be so mild that even the most experienced parents can overlook them. Major developmental problems, such as speech delay, do not become apparent until after children have become old enough to acquire speech.

The bottom line is that the temporal association between the MMR vaccine and autism does not indicate a causal relationship. Just because autism is often diagnosed right after the MMR vaccine is administered doesn't mean that the vaccine triggered the condition. In fact, causal relationship between the vaccine and autism has been repeatedly refuted by many clinical studies.

The Rise of Autism

There are more children with autism today than ever before. This is true even after taking population growth into consideration. Some experts believe that this increase in the number of cases is due to increased reporting. Doctors are more able to diagnose and subsequently report autistic cases to the national database than they were twenty years ago, and this undoubtedly contributes to the overall increase in the number of diagnosed autistic cases. However, most behavioral experts believe that this increased reporting does not completely account for the recent rise of autism.

Unfortunately, it was just as the reported cases of autism were rising that the MMR vaccine was introduced. The fact of the matter is that even though the percentage of children getting the MMR vaccine has not changed significantly over the past ten years, the percentage of children being diagnosed with autism continues to rise. If the MMR vaccine were truly to blame for triggering autism, the rate of autism diagnosis should have remained stable as well. This is not the case.

Lack of Causality

Despite numerous studies attempting to ascertain a causal link between the MMR vaccine and autism, no such relationship has been established. Since no one really knows what truly causes autism, it is impossible to either prove or disprove any hypothesis at this point. However, one thing is certain: If the general population stops receiving the MMR vaccine, a massive outbreak of measles, mumps, and rubella is destined to occur. All three diseases used to kill and disable thousands of children each year before the introduction of this vaccine, and the MMR vaccine has saved millions of children already. Turning back the clock and not immunizing children is simply out of the question.

Some vaccine opponents advocate the practice of separating out each component of this combination vaccine to prevent autism. There is absolutely no scientific evidence that this practice make any difference. However, it does make it exceedingly difficult for children to get these vaccines independently. Most commercial manufacturers stopped making separate vaccines decades ago, and most medical offices do not stock these separated vaccines. The logistical nightmare of obtaining these vaccines just means that your child will fall behind on her vaccinations, which puts her at a higher risk of contracting these dangerous infections.