It’s the myth that just won’t go away: Vaccines cause autism in children.

It’s not true. It’s just not happening.

Yet since 1998, with the Lancet’s publication of the since-retracted work of Dr. Andrew Wakefield, there has been an international debate over the administration of vaccines,in particular the measles-mumps-rubella vaccine,and the development of autism.

There is no link between vaccines and autism.

There’s no reason to refuse vaccinations for potentially life-threatening infections.

Steven Depolo @ Flickr.com

Study after study has looked for the link—they have looked at thousands of children around the world —and found no connection. (If you want a common source, here is a good one that lists 107 studies that concluded that autism and vaccines are not linked. As for a medical source, here is one of many.)

There are three main theories about the supposed link, and they have all been debunked.

The first was proposed by Dr. Wakefield himself in his paper that was published in the British medical journal, The Lancet in the late 1990s. He was a British gastroenterologist, which is a doctor specializing in digestion and the intestines.

He looked at children who already had autism and noted that they had a problem in their intestines. His theory was that the measles-mumps-rubella vaccine, known as MMR, caused the problem in the gut, which then caused autism.

But in a subsequent retraction, he admitted that he manipulated the data to make it look like there was a connection when, clearly, there was not.

The second theory argued that preservatives in the vaccines were the cause of autism. The most common of which was thimerosal, a mercury-based ingredient that was used in vaccines up until the late 1990s.

Thimerosal was never determined to be dangerous, even with a whole childhood course of over 30 immunizations, but as a precaution it was taken out of vaccines.

Despite the elimination of thimerosal, the rates of autism have not changed. In fact, they have increased. In 2014, the Center for Disease Control’s Autism and Developmental Disabilities Monitoring Network reported an incidence of autism that was significantly higher than expected, with one in every 68 children in the country diagnosed. It is far more prevalent in boys, at one in 42, versus one in 189 for girls.

If thimerosal was a cause of autism in children, then eliminating it from vaccines should have led to a decrease in the number of cases that were diagnosed. But the opposite occurred. We no longer use thimerosal, but diagnose higher rates of autism in children.

The third common theory is that too many shots are given too close together, and the immune system can’t handle it.

It might be plausible except that scientists have tested the immune system of those who have received all the usual vaccines and those who have not. They did not find any difference in the body’s ability to fight other common infections.

In fact, the vaccines I got as a child had more than 3,000 different bacterial and viral antigens, which are the parts of the shot that are meant to build up immunity. These days science has improved the vaccines, and fewer than 200 different antigens are used to achieve the same level of immunity.

The sharp decrease in the number of antigens used in vaccines today and the increasing number of cases of autism helps to show that the immune system’s ability to handle vaccinations isn’t really in question.

Refusing vaccinations out of misplaced fear is actually dangerous because it puts our whole community at risk, especially children.

If the problem were that too many vaccines are given too close together, the decreasing number of antigens we use now should have sparked a notable decrease in autism cases. But, as noted earlier, they’ve been rising.

So, is there any reasonable argument to refuse vaccinations for potentially life-threatening infections?

The Centers for Disease Control doesn’t think so.

Refusing vaccinations has a human cost, and it is adding up.

Since January of this year, 580 cases of measles have been reported in 20 states, including Hawaii.

Refusing vaccinations out of misplaced fear is actually dangerous because it puts our whole community at risk, especially children.

The majority of the infections were in people who had refused vaccinations for various reasons. (There is also a risk for people who travel to parts of the world prone to outbreaks of measles —as was made clear by the child in Hawaii who returned from the Philippines in February with the disease.)

For those who are infected with measles, it’s not a benign disease. One out of 20 will get pneumonia, one out of 1,000 will endure encephalitis, which is an inflammation of the brain, and one out of 1,000 will die.

The measles, it is worth remembering, is an entirely preventable disease that was considered to have been eradicated in the U.S. almost 15 years ago.

It is back solely due to inadequate vaccination. In the U.S., this is based on erroneous claims linking the vaccine to autism.

It is worth noting exactly what autism is given that, in the last few years, its definition has expanded. Autism is a brain based disorder that affects a person’s behavior, social and communication skills. It usually appears in children by the age of 3 and remains for life. The “spectrum”of autism includes highly functional individuals, such as those diagnosed with Asperger’s syndrome, those with mild delays and those with more serious developmental disabilities.

Twin studies show that if a person is diagnosed with autism, their twin has an 80-90 percent chance of having autism as well. This strongly suggest genetics are a significant factor.

Given that vaccines don’t cause autism, let’s take a look at what might.

At this point, genetics and the environment are the most likely culprits. It’s already well established that parental behavior is not to blame, so anyone who remembers talk of “refrigerator mothers” from the 1950s can let go of such misguided ideas.

Studies of the brains of people diagnosed with autism that were conducted at the University of California in San Diego showed a myriad of differences, including altered levels of serotonin and other neurotransmitters, as well as changes in the actual anatomy and functioning of the brain.

Twin studies show that if a person is diagnosed with autism, their twin has an 80 percent to 90 percent chance of having autism as well. This strongly suggest genetics are a significant factor.

Recent studies out of UC Davis postulate that exposure to pesticides in utero increases the likelihood of an autism diagnosis by a factor of seven. That retrospective analysis looked at people already diagnosed with autism and the mother’s geographic location during pregnancy. This is not an easy thing to study in a more in-depth way because it isn’t ethical to intentionally expose people to pesticides just to study them.

More research is needed to investigate the causes, but enough money has been spent — or, to be blunt, squandered — on the search for a reason to blame vaccines for autism.

As parents prepare for back-to-school physicals and kids gear up to return to the classroom, it’s time to make sure they are up to date on their vaccinations.

For those who are reluctant, remember, it only takes one child getting sick to start an outbreak among those who haven’t been inoculated.

So don’t hesitate — vaccinate.