No Evidence That Aluminum in Vaccines is Harmful

Part of the anti-vaccinationist stance against immunization is the belief that vaccines contain harmful chemicals such as aluminum, formaldehyde and thimerosal. Although mercury-based thimerosal is no longer used in any U.S. vaccines except certain flu shots, and the amount of formaldehyde is a tiny fraction of that found in many foods – including those fed to babies such as pureed bananas or pears – aluminum remains a villain among the anti-vax crowd. But, as with the discredited link between the measles vaccine and autism discussed in a previous post, no medical evidence exists to support the aluminum hypothesis.


Aluminum salts are employed as powerful adjuvants to enhance the immune system response to a vaccine, thus reducing the number of repeat injections needed. What anti-vaccinationists fail to understand, however, is that less than 1% of aluminum in vaccines is actually absorbed by the body. The same is true of the aluminum found in our food supply, in drinking water and even in the air we breathe, as well as the breast milk or infant formula ingested by babies. For vaccination, the daily quantity of aluminum absorbed by a vaccinated newborn infant is 10 times smaller than the FDA’s threshold for neurotoxicity.

Because it has been suggested that aluminum could be linked to certain neurological disorders such as Alzheimer’s Disease, anti-vaccinationists maintain that injected aluminum rapidly enters the bloodstream and thereby accumulates in the brain, causing neurological damage – reminiscent of Wakefield’s fraudulent claim about autism. There are several scientific fallacies underlying this assertion, however.

The first fallacy is that injected aluminum finds its way into the body more rapidly than ingested aluminum. In fact, most of the aluminum adjuvant in a vaccine remains near the injection site for a long period and is only absorbed slowly into the bloodstream, at approximately the same daily rate as ingested aluminum. Even though the amount of ingested aluminum is much larger, most of that is absorbed in the intestines and only released slowly into the blood.

Another fallacy involves the neurotoxicity of aluminum in the brain. Although aluminum and other chemicals can enter the brain from the bloodstream, they first have to penetrate a protective semipermeable membrane that separates flowing blood from brain tissue, known as the blood brain barrier. The blood brain barrier normally keeps circulating pathogens and toxins from getting into the brain, while allowing the passage of water, nutrients and hormones.

The flawed claim is that injected aluminum sneaks its way into the brain by hiding in macrophages – a type of first-responder white blood cell that devours germs, cellular debris and foreign particles, and plays an important role in the body’s immune system. Unable to digest metals, say anti-vaccinationists, the aluminum-loaded macrophages travel to the brain via the blood or lymphatic system. If the brain is already inflamed, the macrophages can cross the blood brain barrier and unload aluminum inside the brain. The aluminum supposedly causes further inflammation, leading to autism and other neurological disorders.

But none of this makes sense to many doctors and scientists who work in immunology or neuroscience. A neurovascular biologist who’s an expert on the blood brain barrier faults the science in several of the papers behind the Trojan-horse macrophage hypothesis. And he calls out the claim in one paper that macrophages digest injected aluminum as “not only exaggerated … but also provocative and fraudulent,” though this criticism was later accepted as justified on a major anti-vaccinationist website.

The website, whose authors prefer to remain anonymous, claims to be science-based and guided only by scientific evidence – the same as the emphasis of the present blog. The site also attempts to defend itself against charges of cherry picking research papers supporting its position that aluminum adjuvants cause autism. But it merely lists just the abstracts of a handful of the many papers backing the emerging consensus that autism is caused by maternal exposure to infections or toxins during pregnancy.   

In any case, even if the aluminum hypothesis were correct, the fact that the amount of aluminum absorbed from vaccines is comparable to the amount absorbed from aluminum ingested by the body means that macrophages could sweep up swallowed aluminum just as easily as injected aluminum. There’s no good evidence that either occurs, although the mechanisms by which adjuvants act are still not fully understood. 

Hat tip: Mike @realiwasframed

Next week: Politics Clashes with Science over Glyphosate and Cancer

Measles or Autism? False Choice, Says Science

Perhaps nowhere is the attack on science more visible than in the opposition to vaccination against infectious diseases such as hepatitis, polio and measles. To anti-vaxxers, immunizing a child with the measles vaccine is a choice between sentencing him or her to the lifelong misery of autism, or exposing the child to possible aftereffects of a disease that the youngster may never contract. This view, passionately held by a substantial minority of the population, is completely at odds with the logic and evidence of science.


Despite the insistence of anti-vaccinationists to the contrary, there’s absolutely no scientific evidence of any linkage between vaccines and autism. The myth connecting them was first suggested by U.S. activist Barbara Loe Fisher in the 1980s. It gained steam when British gastroenterologist Andrew Wakefield claimed in a 1998 study that 8 out of 12 children in the study had developed autism symptoms following injection of the combination measles-mumps-rubella (MMR) vaccine.

But Wakefield’s paper in the prestigious medical journal The Lancet was slowly discredited until, in 2011, the journal’s editors took the unprecedented step of declaring the paper fraudulent, saying that Wakefield had falsified his data. Die-hard anti-vaccinationists refused to accept this conclusion, despite Wakefield’s medical license being subsequently revoked by the UK General Medical Council, who found that his fraud was compounded by ethical lapses and medical misconduct in the same study.

The autism episode generated worldwide publicity and led to thousands of court cases in a special U.S. Vaccine Court set up as part of the National Vaccine Injury Compensation Program. To cope with the enormous caseload, the court assigned three special masters to hear just three test cases on each of two theories: that autism was caused by the MMR vaccine together with a mercury-based preservative known as thimerosal, or that it was caused by thimerosal-containing vaccines alone.

In 2009 and 2010, the special masters unanimously rejected both contentions. But they emphasized that their decisions had been guided only by scientific evidence, not by the poignant stories of autistic children. One of the masters declared in her analysis:

“Sadly, the petitioners in this litigation have been the victims of bad science, conducted to support litigation rather than to advance medical and scientific understanding of autism spectrum disorder. The evidence in support of petitioners’ causal theory is weak, contradictory, and unpersuasive.”

Yet, despite the Vaccine Court’s findings in the U.S. and The Lancet’s accusation of fraud against Wakefield in the UK, anti-vaccinationists continue to connect the MMR vaccine to autism.  In 2016, Wakefield directed a documentary, “Vaxxed,” alleging that the U.S. Centers for Disease Control and Prevention (CDC) covered up contrary data in a 2004 study that drew the same conclusions as the Vaccine Court and numerous epidemiological studies.  His allegations were baseless, however, as the 2014 research paper behind his outrageous claim was subsequently retracted.

According to CDC statistics, autism spectrum disorder afflicted 1 in 59 U.S. children in 2014. Diagnosis of the condition can be devastating and highly stressful for the desperate parents of an autistic child, who naturally tend to grasp for explanations and are often quite willing to believe the hype about vaccination.  Currently, the causes of autism remain unknown, although several risk factors have been identified: certain genetic conditions have been implicated, and it’s thought that exposure during pregnancy to toxic chemicals such as pesticides, or to bacterial or viral infections, plays a role.

While there’s no medical evidence tying autism to vaccines, it’s also true that serious adverse reactions to a vaccine shot do occur occasionally – typically about once in every one million vaccinations. Negative and occasionally fatal reactions to various vaccines have been documented in approximately 400 research papers. But these 400 cases need to be weighed against the hundreds of millions of vaccine doses administered every year in the U.S. without any reported side effects, cases that aren’t even worth studying.

And the odds of suffering an adverse reaction have to be compared with the risk of contracting the disease itself. One of 1,000 children who get the measles, for instance, will end up with encephalitis, which can have devastating aftereffects such as seizures and mental retardation; some children still die from measles, often after getting pneumonia. It’s a lot less dangerous to subject a child to an MMR shot than risk exposing the child to a disease as contagious and potentially deadly as measles.