What is in a vaccine?

Some of the main ingredients in vacines include:

Antigens – modified, killed, or weakened parts of a disease germ which show our immune system what to fight against if we are ever exposed to the actual disease. 

Adjuvants – tiny, and very safe amounts of chemicals that magnify our immune system’s reaction to the antigen. This makes the vaccine more effective and means that smaller amounts of the antigen can be used. 

Aluminum salts are a common adjuvant that is used in vaccines, and these are also found naturally in almost all foods and drinking water, as well as in breast milk and in formula milk for babies. Aluminium salts are used as food additives (for example in bread and cakes) and in drugs such as antacids, and aluminium is widely used in food packaging. 

Carrier fluid – usually saline or sterile water, this allows the vaccine to be injected.

Preservatives and / or antibiotics – are in some vaccines in tiny amounts that are well-tested for safety. These ingredients keep the vaccine stable and prevent bacteria or other germs growing in the vaccine during storage.


The Oxford Vaccine Group at the University of Oxford have a very helpful and detailed page about vacicne ingredients. You can find it here.