Vaccine Components

Vaccines are made up of a combination of different products. These products are needed to make the vaccine work in your body, and to keep the active parts of the vaccine (the antigens) preserved until they are needed.  Testing vaccine ingredients is a very demanding process, the release of the vaccine is only approved when all components and the way they are used has been demonstrated as safe for human use. Modern vaccines tend to be better than older ones, as they contain less additives and use purer substances.

Vaccines need to have a number of agents added to the antigen to make them a viable and effective pharmaceutical.

What is in a vaccine

• Immune enha​ncer (adjuvant)
• Excipients
• Preservatives
• Stabili​sers
  • Buffe​rs
  • Diluents
  • Residuals

An excipient is usually an inert substance other than the active ingredient included in the manufacturing process or contained in a finished pharmaceutical product. It may be residual in tiny quantities in the final product. 

Actual contents vary depending on the vaccine.

Adjuvants

Most of the NZ schedule vaccines use aluminium-based adjuvants and until recently they were the only vaccine adjuvants licensed for human use. They induce a range of inflammatory factors to the injection site which helps the immune response. They have an impressive safety record with over 70 years of use. Some points about aluminium:

• Eighth most abundant element on earth, most common metallic element
• Found in the blood of all animals, including humans, constantly exposed
• Average daily intake 10-15 mg
• We get rid of aluminium from our bodies in our urine via kidneys
• As an example, hepatitis B vaccine has 0.235 mg of aluminium, water has about 0.2 mg of aluminium per litre
• One dose of hepatitis B vaccine contains less aluminium than one days worth  of baby formula (infant formula has increased aluminium).

Preservatives

Preservatives stop unwanted contamination of a vaccine. The most commonly used preservative is 2-phenoxyethanol. Some points about phenoxyethanol:

• Also used in a range of cosmetics such as baby care products, eye and  ear drops
• Absorbed through skin
• Metabolised (broken down) and excreted by being exhaled, in the urine and in the faeces
• There is little toxicity in humans and some toxicity (irritation) with high doses in animals
• In an experiment a person ingested 11mg of phenoxyethanol and it was excreted in 2-3 days.

Stabilisers

Stabilisers stop chemical reactions from occurring in the vaccine and prevent the components from separating from each other. A common stabiliser is gelatine (as in jelly). Other products include amino acids (the building blocks of proteins).

Buffers

A buffer solution is one which resists changes in pH when small quantities of an acid or an alkali are added to it. Buffers keep the vaccine at a similar pH to the body. Often the buffer will be a salt.

Adjusting tonicity

To keep the vaccine isotonic (to reduce local reactions) a salt may  be added. Often this will be Sodium Chloride (common table salt).

Surfactants and emulsifiers

These are wetting agents that act a bit like a detergent. A commonly used surfactant is called Polysorbate 80 or Tween®. This is made from sorbitol (a sugar alcohol) and Oleic acid (an omega fatty acid). Polysorbate is often used in foods such as ice cream.

Residual substances

Sometimes there are traces left of ingredients used during the manufacturing process.These are not part of the final formulation but can be measured, usually in parts per million or billion (ppm, ppb). Such components are:

• Components of growth media such as proteins such albumin, vitamins and amino acids, extracts such as yeast
• Albumin is a water soluble protein, usually from serum or egg used in growth media during the culture process
• Antibiotics such as neomycin and streptomycin – preventing contamination, usually during the manufacture process
• Formaldehyde – used in the inactivation of viruses and toxins during manufacture.

Formaldehyde

Formaldehyde is irritating to tissues at 0.4-3 ppm and becomes dangerous at 20 ppm. It is found in all our bodies in tiny amounts and is required for the synthesis of DNA. Exposure to formaldehyde occurs daily in the environment from pollution, some foods such as cheese and fish, many household products such as building materials and furniture. Formaldehyde breaks down very quickly both in the environment and in the body. It does not build up and is not stored.

The average infant has at least 5 times more formaldehyde in their bodies than is present in a vaccine. Quantities of formaldehyde 600x greater than that found in vaccines are considered safe.

Toxicological Profile for Formaldehyde July 1999. Agency for Toxic Substances and Disease Registry. United States Public Health Service