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No, mercury and aluminium are not toxic when used in vaccines

A claim circulating on social media in late 2022 suggests that mercury and aluminium, used as additives in vaccines, are “extremely toxic when injected”.  

Other versions of the claim appear on Facebook here and on Twitter herehere, here, here, here and here. Some posts have received thousands of views and likes. The posts all include a video claiming to show the chemical reaction between mercury and aluminium. 

The video snippet is from a 2021 YouTube video by Home Science, and does show this chemical reaction. But it has nothing to do with vaccines or their ingredients, as Associated Press News explains in their fact-check here.

So what about the claim that mercury and aluminium, used as additives in some vaccines, are toxic when injected? We looked into it. 


Aluminium used as a vaccine adjuvant – and widely in everyday life

When manufacturers develop a vaccine, they often add ingredients that help strengthen the immune system’s response to the vaccine, making the vaccine work better. These ingredients are called adjuvants

Aluminium salts have been used in vaccines for over 70 years, according to the US Centers for Disease Control and Prevention (CDC). Originally used in tetanus and diphtheria vaccines, they are often also used in vaccines for hepatitis A and B, some influenza vaccines, and pneumococcal vaccines, among others.  

Although it may sound alarming for aluminium to be in a vaccine, it is actually all around us in everyday life too. According to the European Food Safety Authority, aluminium is produced by and used for “water treatment, papermaking, fire retardant, fillers, food additives, colours and pharmaceuticals”. 

Small amounts of aluminium are in “almost all” food and drinking water, according to the University of Oxford. Some foods, such as baked goods and particular vegetables, have higher levels than other foods. When the body absorbs this aluminium, it is flushed out of the body via the kidneys. 

High doses of aluminium, just like high doses of most substances, can cause health problems, according to the US government’s Agency for Toxic Substances and Disease Registry. For example, workers who are exposed to large amounts of aluminium dust can develop respiratory problems, and people with kidney disease store more aluminium in their bodies, which can lead to bone or brain diseases. 

Historically, some research suggested there may be a link between high levels of aluminium and Alzheimer’s disease, but there is not enough evidence to support this idea. Some other studies suggested that the aluminium in vaccines could be linked to autism spectrum disorders. But these studies were found to be “seriously flawed” by the World Health Organization’s Global Advisory Committee on Vaccine Safety

And research into aluminium-containing infant vaccines suggests that being exposed in this way carries “extremely low risk", even for babies. Since they first started being used in vaccines in the 1930s, aluminium salts have not been a cause for concern among medical professionals. The amounts used are considered too small to be dangerous, and they aren’t easily absorbed by the body, the CDC confirms.

Mercury-containing vaccines – different forms of mercury with different effects 

Another adjuvant that historically was often used in vaccines is thimerosal. This ingredient contains ethylmercury, a form of mercury, which prevents harmful bacteria growing in vaccines, according to the CDC.

Given that mercury is known to be a toxic chemical, some people may be concerned about getting vaccines with an ingredient that contains mercury. High levels of one type of mercury have been linked with cognitive impairments and brain damage

These impairments looked similar to those shown by children with disorders on the autism spectrum, which led to worries that mercury-containing vaccines were a cause of autism spectrum disorders, despite no evidence showing this. 

Before research was done, it was assumed that both forms of mercury were similarly toxic. As a precaution, thimerosal was removed from most vaccines, “in line with the global goal of reducing environmental exposure to mercury from all sources”, according to the University of Oxford.

But there is now lots of data showing that the two forms are very different, the CDC says. While methylmercury builds up in the body and can be very dangerous in high doses, ethylmercury is cleared from the body quickly, even in young infants. 

Since the concerns about methylmercury were first raised, and the controversy around vaccines and autism, a lot of research has been done to make sure that ethylmercury in vaccines was not causing any harm. 

In the early 2000s, a scientific review by the Institute of Medicine (now the National Academy of Medicine) found that all the evidence showed no causal link between thimerosal vaccines and autism. Since then, the CDC has done numerous studies and come to the same conclusion: vaccines containing thimerosal do not cause autism. The WHO and CDC agree that the ingredient is not dangerous in other ways either. 

One side effect of vaccines that contain adjuvants is they can cause more minor swelling, pain and redness at the injection site, compared with vaccines that do not contain adjuvants. They can also cause more fever, chills and body aches. But this does not mean they are toxic. 

“Vaccines containing adjuvants are tested for safety … and they are continuously monitored by the CDC and FDA once they are approved,” the CDC said

There is no reason to worry that aluminium and mercury in vaccines will react in your body like they do in the video posted on social media.

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