What else is in a vaccine?
Vaccines can contain other ingredients that are added to help stimulate a stronger immune response or to help the biological material remain stable for longer. These can include preservatives, stabilisers and adjuvants. There can also be trace materials left over from the manufacturing process. All ingredients added to a vaccine must be approved for use by regulators after safety testing.
Manufacturers must list all of the ingredients in a vaccine on patient information leaflets. You can also ask your doctor what is in your vaccine.
Here are some of the additional ingredients you can find in vaccines:
- Preservatives: These can help to prevent vaccines from becoming contaminated after the vials they are stored in have been opened. Common preservatives such as 2-phenoxyethanol have a long history of safe use. Thiomersal is a preservative which is not widely used in current vaccines and has not been used at all in any vaccine in the UK since 2005.Thiomersal contains very small amounts of a type of mercury called ethylmercury. Although mercury is known to be toxic, ethylmercury is cleared from the body within 30 days and no evidence of harm has been found after decades of use. No link between thiomersal and neurodevelopment disorders such as autism has been found despite extensive research.
- Stabilisers: Ingredients such as lactose, gelatine, sorbitol and glycine are sometimes added to help protect the vaccine and to keep it from sticking to the inside of the bottle it is stored in. Emulsifiers such as polysorbate can also sometimes be added to keep all the ingredients mixed together. All of the above additives are commonly used in many food products.
- Adjuvants: These are added to some vaccines – particularly sub-unit vaccines – to stimulate immune cells and boost the immune response generated by the vaccine. Common adjuvants include small amounts of aluminium salts such as aluminium hydroxide, aluminium phosphate and or potassium aluminium sulphate. These are present in several vaccines used today including those for hepatitis A and B, and some meningitis vaccines. Adjuvants can lead to slightly higher levels of redness and hard lumps at the injection site. Studies have shown that the amount of aluminium received from vaccines is less than is absorbed from a typical diet and well within safe weekly intake levels.
- Trace materials: There can be low levels of residual material left in some vaccines from the manufacturing process. This can include egg proteins, antibiotics or yeast proteins. These are usually of no consequence, unless the recipient has a strong allergy to those substances. Some vaccines can also contain other animal products, such as porcine gelatine, which comes from pigs. There are three vaccines in the UK that currently contain porcine gelatine – the Fluenz nasal spray given to children to protect against flu; the MMR VaxPro against measles, mumps and rubella; and the ProQuad MMRV vaccine against measles, mumps, rubella and chickenpox. These products are considered to be permissible in non-oral vaccines under Jewish law according to the Kashrut and Medicines Information Service, while some Muslim scholars have similarly said these are permissible. There are also alternative vaccines that do not contain porcine gelatine