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Disclaimer: I work on HIV vaccine design and I'm quite proud of it. I know that for three million HIV-positive kids in Africa, a vaccine is the only hope they have to grow into adulthood. So, when people tell me that vaccines are bad I cringe. Infant mortality rates have dropped since vaccinations have been introduced. We live longer, healthier lives thanks to vaccines. Diseases like polio can paralyze and kill, yet they are no longer a concern for children in the western world.
At the same time, I'm fully aware that medicine is not a science. When it comes to the human body, there are no certainties. We use statistics to measure effects, but statistics do not give you a yes/no answer: they give you averages, trends, probabilities. And as parents, we need to make decisions for our kids, not for the average child.
So, when my friend Autumn Kalquist asked me about aluminum and vaccines, I started digging up the literature right away.
In layman terms, this is how a vaccine works: the goal is to teach the immune system to recognize a certain pathogen, whether it is a virus, a bacteria, or a cancer cell. To do so, we take bits of proteins from the pathogen and we make sure that the immune system sees them. Since it's not the whole pathogen that's injected inside the organism, but only some of its proteins, the pathogen cannot mount an infection. On the other hand, the immune system will recognize the proteins as "extraneous" and will start making antibodies able to bind to them. The beauty of this mechanism is that once the immune system finds an antibody that perfectly matches the extraneous protein, the information will be stored in its "memory." Next time the immune system will come across the same protein -- this time from the whole pathogen -- it will be able to retrieve the "memory" of the right antibodies to use against the proteins. the antibodies will bind to them and initiate the process that leads to the destruction of the pathogen.
While the principle seems "straightforward", there are many obstacles to overcome when designing a vaccine. The first one of course is to select the right proteins that will elicit a strong enough immune response. This has proven particularly challenging in HIV because of the virus's extreme variability. Since no two viruses are identical, proteins from one particular virus are never enough to mount a response that's protective against all kinds of HIV strains.
But even when the virus is not as variable as HIV there are other challenges: the fact that you inject something inside the body doesn't automatically guarantee that the immune system will see it. In some cases the pathogen proteins alone are not enough to recruit a strong enough immune response. In these cases, additional molecules are added to the vaccine: these molecules, called adjuvants, are able to initiate signals that in turn alert the immune system to recruit lymphocytes.
And this is where we get to the controversy: many effective adjuvants contain aluminum, which for some has been a cause for concern. Though aluminum is quite efficient at stimulating the immune system, in high doses it can cause serious neurodevelopment damage. This is particularly true for small children since their growing brains are more permeable to toxic substances.
Are vaccines containing aluminum safe, then?
First of all, let me say that I'm appalled that the question is raised with regards to vaccines, but nobody seems to take notice that tattoo ink contains aluminum, too. I guess tattoos never had the pretense to save lives. So while it's not worth taking chances with aluminum to save a life, it's totally worth doing it in the name of skin branding?
Back to vaccines: as it often happens when you try to address such questions, you start digging for information and you find both "yes" and "no" answers.
People who think they are safe tend to reason that (1) they've been used for over seventy years and by now we would've noticed if they weren't; (2) we are constantly exposed to aluminum since it is found in many foods, food additives and in foods prepared with aluminum utensils.
But you'll also find people who quite adamantly state that aluminum containing adjuvants are not safe since the vaccine doses are higher than the recommended IV solution doses. My friend Autumn brought to my attention Dr. Sears' position and questioned the comparison he makes:
The first document (see Resource 1) I came across discusses labeling of aluminum content in injected dextrose solutions (a sugar solution added to IVs in the hospital). [. . .] The second document (see Resource 2) discusses aluminum content in IV feeding solutions (called TPN). The FDA requires these solutions to have no more than 25 micrograms of aluminum in each liter of solution.Currently used vaccines contain between 125 and 850 micrograms.
So, who's right?
The first thing one should do when setting off on a quest like this is make sure that we are comparing apples to apples and oranges to oranges. The arguments above are both wrong because the aluminum contained in vaccines is administered through intra-muscular injection, which is quite different than ingesting it with foods or receiving it through an intra-venous solution. In other words, both arguments above are comparing apples with oranges.
Aluminum in food might be safe to consume because our guts tend to be a quite efficient barrier that will ensure that not all of it will be absorbed into the bloodstream. On the other hand, as Autumn rightfully noticed, it's incorrect to compare intra-venous dilutions to intra-muscular injections: intra-venous solutions better have the lowest possible doses of aluminum since whatever you gets injected immediately enters the blood flow.
Animal studies have shown that aluminum administered through intra-muscular injections can take up to a month to be released into the blood stream . This slow release and clearance ensures that at any given time during that month the circulating levels are much lower than the total level of aluminum contained in the original dose. In fact, in , author HogenEsch cites studies that have found aluminum based vaccines to induce fewer local reactions than vaccines without the adjuvant, a phenomenon that could be due to the fact that aluminum stimulates the immune response (which is why it's used in vaccines in the first place).
To play devil's advocate I also found a paper that, contrary to HogenEsch's review, raises a red flag against aluminum adjuvants. The authors, Tomljenovic and Shaw , compared ASD (autism spectrum disorder) prevalence from the US, UK, Australia, Canada, Sweden, Finland and Iceland, and contrasted it with the cumulative aluminum doses received through childhood vaccinations in each country. The authors found a strong correlation between cumulative exposure to aluminum through vaccines and higher ASD prevalence, and claimed that, based on Hill's criteria, this correlation is a strong statement in favor of causation.
Let's pause for a moment and make one thing clear: correlations DO NOT PROVE causation. A classical example is the correlation between crime rates and ice cream sales: they seem to rise at the same time during the year, and that time of the year happens to be summer. But it's pretty obvious that ice cream sales do not cause a rise in crime rates. However, the researchers in  argue that:
"The positive correlation between Al exposure from vaccines and prevalence of ASD does not necessarily imply causation. However, if the correlation is strong (criterion 1), consistent (criterion 2) and ifThe above discussion is sensible, but it still does not take away the fact that the correlation they've found DOES NOT prove causation. The only way you could prove a causal relationship here would be to have an animal model and an experimental setting with several groups receiving increasing doses of aluminum. You then measure the prevalence of ASD in each group. Until we have such an experiment we cannot rule out the multiple factors that could possibly bias this correlation. For example, ASD diagnoses have been rising in the past decades because of better diagnostics tests.
there is a biologically plausible mechanism by which it can be explained (criterion6),as well as an appropriate temporal relationship between the proposed cause and the outcome (criterion 4), then the satisfaction of these criteria supports the notion that the two events may indeed be causally related. Our results satisfy not only all four of these criteria applicable for establishing causation in neuropsychiatry,but also four others. These additional criteria are: (5) biological gradient, (7) coherence with the current knowledge, (8) experimental or semi-experimental evidence and (9) the analogy with similar evidence ."
At the same time, while Tomljenovic and Shaw DO NOT PROVE that aluminum adjuvants cause autism, they do raise some interesting points. The adjuvants are needed because without them the vaccines are not effective. However, part of the problem is that immune responses in infants under 6 months of age are weaker. Those are also the most delicate months from the neurodevelopment perspective, making the organism more fragile to aluminum exposure. So maybe one needed intervention could be to revisit the vaccination schedule in infants. I'm not a medical doctor, so I can't make any recommendations, but, as a parent, I do wonder: is it strictly necessary to vaccinate infants starting from their first day in the world as it's done in the US? Could we maybe wait a few months? Would this be too dangerous for babies in nurseries?
While none of this discussion brings a definitive answer, I hope it does provide food for thought. Clearly, if these adjuvants have been used for over 70 years, the vast majority of the population can tolerate them pretty well. The problem, of course, is that as parents, our children are not "the vast majority." They are individuals and we want the very best for them. I think that there is a lesson to learn here. First, we need more dialogue between the researchers, the medical providers, the FDA, and the parents. The debate lately has been too "black and white", whereas any time I try to dig into the literature I see too many grays. This is not a matter one can address with a definitive yes or a definitive no. My best advice is: (1) don't limit yourself to one opinion only, not even when it comes from a reputable source; (2) read a lot, read from all sources, and then use your best judgement based on your family history and your children's health history; (3) allow yourself some leeway. For example, if a stronger vaccine is necessary under 6 months of age, if there is a family history of ASD, it may be worth considering the pros and cons of delaying the vaccine schedule. Or maybe start off with the non-aluminum vaccines, like polio, for example.
And remember: your decision will affect not just your kids but also, to some level, the rest of the population. If you have a family history of ASD and/or immunological problems, by all means, take precautions. Your kids will still be protected by the phenomenon called "herd immunity" so long as the majority of the population keeps getting vaccinated. For the rest of us, the fact that vaccines have benefitted us all as a population should be undeniable.
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 Hogenesch H (2012). Mechanism of immunopotentiation and safety of aluminum adjuvants. Frontiers in immunology, 3 PMID: 23335921
 Tomljenovic L, & Shaw CA (2011). Do aluminum vaccine adjuvants contribute to the rising prevalence of autism? Journal of inorganic biochemistry, 105 (11), 1489-99 PMID: 22099159