Adjuvants are substances that are used to enhance the effects of some vaccines. They are used in inactivated vaccines, such as the influenza vaccine, because the immune system would not give a sufficiently strong reaction to the components of the pathogen in the vaccine on their own.

Adjuvants make the immune response stronger. They can cause side effects, e.g. pain and hardness at the injection site, but these are usually not serious.

The mRNA and vector vaccines do not contain adjuvants. Other vaccines, such as the so-called inactivated vaccines, can contain different adjuvants.

Further information on the use of adjuvants in vaccine development is available from vfa (Germany's association of research based pharmaceutical companies) and in an article in the journal Pharmazeutische Zeitung.

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