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Autism and vaccines: correlation is not causation

by Donald Prothero, Jan 22 2014

Just after the beginning of the year, leading anti-vaxxer and former Playboy Playmate Jenny McCarthy was in the news again. Several years ago, she apparently told Time magazine that her son Evan didn’t have autism, but (as doctors have long suspected) Landau-Kleffner syndrome. Then in January, McCarthy made several angry denials of this old interview. Frankly, I doubt that a source like Time magazine misquoted her—I think she’s lying again. She now claims that Time magazine inaccurately reported the facts! I think my irony meter just broke. Jenny McCarthy was a washed-up actress with nothing but a series of low-brow movies and TV shows to her credit until she became the national spokeswoman for the anti-vaxxer movement—a movement which was,  in a form of supreme irony, legendary for an inaccurate grasp of the facts, then shifting the goal posts on their demands when the mercury was removed from the vaccines and there was still no effect on rates of autism. She rejects mainstream science, yet cites biomedical science in support of her claim that her son really has autism. I think we should reject her claim outright, because she (like many anti-vaxxers) have no clue what mainstream science and medicine are about.

Now she and her anti-vaxx cohort are demanding that medicine and drug companies should “green the vaccine”! What the heck do they think the FDA is for? All vaccines must pass rigorous testing and quality control through the FDA, which has one of the most stringent standards for drugs and medicine in the world. Fat chance that she and her fellow science-denying protesters are going to help the process in any way! Meanwhile, she’s now on The View every day, giving an air of legitimacy to her form of pseudoscience. And the movement she bolstered is causing huge numbers of kids to go unvaccinated, get sick and sometimes die of preventable diseases—and, even worse, spread those diseases to and often kill infants too young for vaccination (even if their parents do believe in modern medicine). Continue reading…

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Legal Courts And Science

by Steven Novella, Jul 29 2013

Facebook is like a graveyard in a zombie movie, where old news items rise from the dead to have a second life. I am often asked about news items that are burning up Facebook, only to find that they are years old, but never-the-less they have to be addressed all over again. ]

One such item (actually a few items) is a 2012 news report about the Italian courts awarding money to the Bocca family a large reward because it concluded their 9-year-old son acquired autism from the MMR vaccine.

History here is a useful guide. The courts have historically often been out-of-step with the science, tending to err on the side of awarding compensation for possible harm. For example, until about the 1920s it was thought that physical trauma could cause cancer. Animal studies and epidemiological evidence, however, showed that there was no causal connection. Recall bias and increased surveillance were likely the cause of the apparent association.

Continue reading…

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Early Detection of Autism

by Steven Novella, Jan 30 2012

Autism is a spectrum of neurological disorders that involve, primarily, reduced social aptitude. People with autism tend to make less eye contact, they have less of a response to viewing a human face, and they are less verbal. Half a century ago autism was blamed on bad parenting, but that view is now considered outdated and even cruel.

Autism is a brain disorder. Neuroscientists are learning more and more about what is different about autistic brains from more typical brains. One feature seems to be reduced communication among neurons in the brain. Autism is diagnosed clinically. It is usually first recognized by the parents, who then bring their child to medical attention and after an evaluation the diagnosis is made. At present there are no supporting laboratory tests – we don’t diagnose autism by an MRI scan, EEG, or blood test. It is diagnosed by clinical observation and some standardized questionnaires and cognitive tests. At the more subtle end of the spectrum the diagnosis may not be made right away, not until the child is a bit older and can be more thoroughly evaluated.

The median age at diagnosis was 4.4 years in 1992. This has steadily decreased, to less than 3.4 years by 2001. This effect is greater in higher socioeconomic status (SES) groups. Low SES children are diagnosed later than higher SES children, and this gap has widened in the last 20 years. There has also been a linear increase in the number of autism diagnoses since 1992, aggregating in birth cohorts, with a greater effect for higher functioning children with autism. This suggests that more diagnoses are being made at the milder end of the autism spectrum, and at a younger age, with a strong social influence. Continue reading…

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The Long Awaited CDC Trial on Thimerosal and Autism

by Steven Novella, Sep 13 2010

We can add one more study to the pile of evidence showing no association between exposure to thimerosal (a mercury-based vaccine preservative) and autism. The article: Prenatal and Infant Exposure to Thimerosal From Vaccines and Immunoglobulins and Risk of Autism, is published in the latest issue of Pediatrics, and shows no association between prenatal and infant exposure to thimerosal and three forms of autism – autism, autism spectrum disorder, and regressive autism.

No one study can ever be definitive, but now we have a large body of evidence from multiple studies showing a lack of association between thimerosal and autism. This won't stop the dedicated anti-vaccinationists and mercury militia from continuing their anti-vaccine propaganda, but hopefully it will further reassure those who actually care about the science.


This has been a long and complex story, so let me review some of the background. Diagnosis rates of ASD have been climbing for the last 20 years, prompting some to search for an environmental cause. The existing anti-vaccine community, not surprisingly, blamed vaccines. This was given a tremendous boost by the now-discredited study by Andrew Wakefield concerning MMR (which never contained thimerosal) and autism. When the evidence was going against MMR as a cause, attention turned to thimerosal in some vaccines. This notion was popularized by journalist David Kirby in his book, Evidence of Harm.

Continue reading…

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Autism and Vaccines Taken On By Matt Lauer

by Kirsten Sanford, Aug 28 2009

This Sunday before game-time you might want to set your Tivos to record Dateline. This week, supposedly, Matt Lauer interviews Dr. Andrew Wakefield and several other affiliates of the Thoughtful House Center for Children, along with Dr. Paul Offit and journalist Brian Deer.

The Thoughtful House agreed to the interviews because they figured they would get fair treatment from the likes of Matt. I’m interested to see what kind of a program NBC has put together on this very sensitive subject.

Depending on how this major media outlet writes the script, it could either be a major affirmation of what many within the science community already know, or it could increase the divide between anti-vax’ers and science.

Please, Matt… don’t go Jenny McCarthy on us. Don’t do the usual journalistic job of being “fair-and-balanced”. This is not a “he said, she said” issue. This is science. Do tell the world what the science supports.

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Were the original data linking vaccines and autism faked?

by Phil Plait, Feb 11 2009

The UK-based Sunday Times has a potential bombshell on their site; they claim Dr. Andrew Wakefield, who started the whole "vaccines cause autism" garbage, faked his data to make that claim.

About 10 years ago, Wakefield published a study dealing with children who were autistic, developing symptoms shortly after getting their shots, and linked this with irritated intestinal tracts. This study came under a lot of fire, and eventually most of the authors retracted the conclusion that autism was associated with "environmental factors", that is, vaccinations. By then, though, it was too late, and the modern antivaccination movement was born.

The Sunday Times investigated Wakefield’s original research, and alleges that the symptoms Wakefield reports in his research do not match hospital records of the 12 children studied at the time. In only one case were there symptoms that arose after the injection; in many of the other cases symptoms started before the children had been vaccinated (in fact, there have been allegations for some time that neurological issues occurred in the children before they had actually been vaccinated, casting doubt on Wakefield’s work). Also, hospital pathologists reported that the bowels of many of the children were normal, but Wakefield reported them as having inflammatory disease in his journal paper.

Continue reading…

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Skeptical Battlegrounds: Part IV – Anti-Vaccine Hysteria

by Steven Novella, Dec 22 2008

There is a dedicated fringe anti-vaccine movement. They are dedicated to some permutation of the collection of beliefs that vaccines are: 1) not effective; 2) have not reduced or eliminated any infectious disease; 3) are not safe; and 4) are a conspiracy of Big Pharma, the government, and paid-off doctors. Specific claims have wandered over the years, but they have as a central theme that vaccines are bad. When one specific claim collapses, they will move on to the next anti-vaccine claim.

While anti-vaccine cranks have been around as long as vaccines, it is only recently that they have captured the attention of the mainstream media and the skeptical movement and the battle has really been engaged.

Anti-vaccinationists have focused much of their recent efforts on the claim that vaccines cause autism. At first the MMR vaccine was blamed, sparked by a now-discredited study performed by Andrew Wakefield. This led to declining vaccination rates in the UK and a resurgence of measles.

As the MMR claim was in decline (although by no means abandoned), attention shifted to thimerosal – a mercury-based preservative in some vaccines. There are many flaws with the thimerosal hypothesis, and numerous studies have shown no link between thimerosal and autism or any neurological disorder. But the fatal blow to the thimerosal hypothesis was struck when thimerosal was removed from the routine childhood vaccine schedule (thimerosal, incidentally, was never in the MMR vaccine) in the US by 2002. In the subsequent 6 years the rate of autism diagnoses kept increasing at their previous rate, without even a blip. Only the most rabid (or scientifically illiterate)  anti-vaccine fanatics still cling to the thimerosal claim. Continue reading…

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