Adjuvant

A substance included in some vaccines to strengthen or shape the immune response to their antigens. Adjuvants can improve responses when an antigen alone produces insufficient immunity.

Pattern recognition receptors: Immune receptors that detect microbial molecules and signals of cellular damage. Several adjuvants activate these receptors, prompting innate signals that help initiate adaptive immunity.
MF59: An oil-in-water emulsion adjuvant used in some influenza vaccines. It demonstrates how an emulsion can enhance responses to influenza antigens.
Vaccine: A preparation that trains the immune system to recognize a pathogen or its products. An adjuvant is one component of some vaccines, alongside the antigen and other formulation ingredients.
Adjuvant-free vaccine: A vaccine formulation that contains no added immune-enhancing adjuvant. Some vaccines generate adequate immunity without an adjuvant, unlike formulations designed to boost weaker responses.
Aluminum salts: Aluminum-containing compounds used as adjuvants in many human vaccines. They are the most familiar adjuvant class and illustrate how formulations can enhance antibody responses.
AS01: A liposomal adjuvant system containing monophosphoryl lipid A and QS-21. Its combination of immune stimulants supports the strong response in the Shingrix vaccine.
Antigen: A molecule or molecular structure that can be specifically recognized by antibodies or immune receptors. The vaccine antigen is the target whose immune response an adjuvant modifies.
Live attenuated vaccine: A vaccine made with a weakened pathogen that can replicate without causing disease in most recipients. Live attenuated vaccines often supply their own innate immune stimulation rather than relying on an added adjuvant.
Toll-like receptors: A family of pattern-recognition receptors that detect microbial components and trigger immune signaling. Adjuvants such as monophosphoryl lipid A stimulate these receptors to shape vaccine responses.
Shingrix: A recombinant vaccine used to prevent shingles in adults. Its efficacy depends on the AS01 adjuvant paired with the varicella-zoster virus glycoprotein E antigen.

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