What are vaccines made of?

The single most crucial component of a vaccine is the antigen mixed with adjuvants, diluents, stabilisers, and preservatives. These components play different supporting roles in preserving the antigen. Also, the vaccine may contain some residues of substances used to create antigens.

What are antigens?

Antigens are commonly made up of fragments of germs that are dead or weakened or by-products of the germ, such as toxins. Antigens have the remarkable characteristic of teaching your immune system how to flush out germs such as viruses or bacteria before you become sick from them.

Some vaccines contain more than one antigen, for example, from different germs, thus making it easier to protect against multiple diseases with less pain.

What are adjuvants?

Adjuvants boost your immune system's response to the antigens in the flu vaccine. This can reduce the number of injections needed for full protection, making vaccination less painful.

Common adjuvants include potassium aluminium sulphate, aluminium sulphate and aluminium hydroxide, and salts often referred to as 'alum'. It's worth noting that the actual aluminium content in vaccines is minimal.

What are diluents?

Diluents make up a large part of any flu vaccine. Vaccines may also contain diluents such as saline or sterile water. These components do not affect the body and are included to ensure that the vaccine contains the smallest useful dose.

What are stabilisers?

Stabilisers are substances such as oils or sugars that help prevent the antigen from sticking to the sides of the container (i.e. the syringe or needle).

What are preservatives?

Preservatives are used to maintain the vaccine's integrity and prevent it from becoming contaminated with fungi or bacteria. Alcohol is often the preservative of choice, replacing thiomersal as the main preservative in children's vaccines in Australia.

What are residues?

Residues are minuscule amounts of leftover by-products used to create the antigen. They are considered harmless as most are already present in our bodies. An example of a residue is formaldehyde, used to inactivate viruses.