Apart from the active part of the pathogen, the vaccines also contain several other ingredients which are essential to facilitate immune response and are safe for human usage.
Vaccines have preservatives which protects the vaccines from being contaminated. Usually one-dose vials do not have preservatives as they are used in a single time on a single human being. Vaccines which are used to vaccinate more than one person have preservatives in them. 2-phenoxyethanol is a commonly used preservative in vaccines. This chemical is not toxic to human beings.
Adjuvants are added to some vaccines to improve the immune response. These are also called immunopotentiators. Aluminium salts (like aluminium phosphate, aluminium hydroxide or potassium aluminium sulphate) are usually used as adjuvants.
Surfactants are also used in order to keep the vaccines together instead of clumping of particles.
Sterile water or diluent is also used in vaccines to bring the concentration of vaccine to optimum level for use.
Sugars, gelatins and proteins are used to stabilize the vaccine and prevent chemical reactions from happening and keep the vaccine from sticking to the vial.
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