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Hem What do vaccines contain? Is aluminium, formaldehyde or mercury present in vaccines?

What do vaccines contain? Is aluminium, formaldehyde or mercury present in vaccines?

What do vaccines contain?

This post is also available in: Svenska

You are one of many who have asked for a post about what’s inside a vaccine. Others wonder why there is aluminum and formaldehyde in vaccines. A few more have heard that mercury is added as a preservative in vaccines. And what exactly is an adjuvant? Vaccines essentially consist of infectious agents (live, dead, or parts of infectious agents), which are supposed to stimulate the immune system to form protection against bacteria or viruses.

You can read more about how vaccines work here.

Additives in vaccines are therefore the substances that are not viruses, bacteria or parts thereof. Their role is to create a stronger immune response in people receiving the vaccine ie. they help vaccines work better. Let’s go through these one by one.


Aluminium is used in several vaccines to increase immune activation. When aluminium is used, many more vaccinated people will form an immunological memory against the infectious agents. Therefore aluminium enhances the effect of the vaccine by assisting in immunological memory and creating herd immunity.

The immune system can react non-specifically to substances that do not belong in the body, such as aluminium. The non-specific or innate immune reaction stimulates the specific or adaptive immune reaction. This is where T- and B- cells create immunological memory. The immunological memory prevents infectious diseases and its spread, the sole purpose of vaccinations. (A substance that increases immune system activation in this way is called an adjuvant).

The amount of aluminium in the vaccine is very small. A child fed on formula receives the same amount of aluminium in two days, as they would a dose of vaccine. However, absorption via the intestine is different to injecting into the muscle. To reduce the amount of aluminium given to the child, combination vaccines with diphtheria, tetanus, whooping cough, hepatitis B, Haemophilus influenzae type B and polio are given in the same syringe. One aluminium dose is sufficient to be given concurrently with 6 vaccines as a combination vaccine. How cool is that!

Aluminum can, in very rare cases, cause local hypersensitivity reactions at the injection site. This comes up as as itchy, red nodules. In those affected, the hypersensitivity reaction can recur when using aluminium on the skin, for example in the form of deodorants later in life.

Aluminium is included in vaccines against tetanus, diphtheria, pneumococcus and Haemophilus influenzae type B and in TBE vaccines.


Formaldehyde is used in the manufacturing of inactived or dead vaccines. Formaldehyde kills viruses (like in the polio and TBE vaccines) or weakens the infectious agents so that it cannot cause disease (like in the diphtheria or tetanus vaccine). Formaldehyde may cause contact allergies. However there is no evidence that a formaldehyde allergy will develop later in life (unlike an aluminium allergy, where this has happened, but is rare).

Formaldehyde is also found in very small doses in vaccines. Not known by many, but formaldehyde is released from furniture and tobacco smoke. A baby inhales as much formaldehyde in a dose of vaccine, as they would by just staying indoors between 4 to 40 hours.

Albumin and gelatin

Human albumin is a protein extracted from the blood of donors. Gelatin is extracted from the connective tissue of pigs. Albumin and gelatin are used as stabilizers in some vaccines.

Residues of culture medium

When growing cells, viruses or bacteria, they require a culture medium. It is a soup with nutrients and salts that is specially composed for that specific kind of organism to be grown. In addition, antibiotics are usually added to the culture medium when growing viruses, so that bacteria do not grow.

In combination vaccines against diphtheria, tetanus, whooping cough, polio and Haemophilus influenzae type B, there are residues of culture medium because it cannot be completely purified. In vaccines against measles, mumps and rubella, (a live vaccine, unlike the previous vaccine I mentioned), the culture medium is present to keep the vaccine viruses alive.

No mercury in the vaccines under the Swedish National Immunization Program

From the 1950s, a mercury-containing preservative (thiomersal) was used in several vaccines. There is a scientific consensus that the doses in vaccines have been so low that they are most likely not harmful to children’s development. Due to the risk of hypersensitivity reactions (allergic reactions), mercury-containing preservatives have been removed from more and more vaccines. The Swedish National Immunization Program has been mercury-free since 1992-1993.

The vaccines against TBE (Encepur and FSME immune) and chickenpox are also mercury-free.

All posts about vaccinations can be found here.

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