What Are Adjuvants?

An adjuvant is an ingredient used in many vaccines to create a strong and targeted immune response.  Adjuvants are designed and proven to enhance the vaccine’s effectiveness.

Vaccine adjuvants create, accelerate, target, enhance and prolong the immune responses to antigens—the vaccine components that provide disease-specific immune information. People with compromised immune systems, such as the elderly and infants, particularly benefit from vaccines with adjuvants because their immune systems may require an extra boost to provide protection. Adjuvants allow vaccine developers to use less antigen, which in some cases may be in short supply or costly.  Adjuvanted vaccines can elicit more durable immune responses, reducing or eliminating the need for booster vaccinations.  Many potent adjuvants and combination adjuvants are currently derived from saponins.

Saponin Adjuvants

Saponin adjuvants are potent immune stimulators typically derived from plants, like soapbark (Quillaja saponaria) trees and soapwort.

Saponin adjuvants, which include QS-21 and Matrix-M®, are manufactured using natural material harvested from the inner lining of the bark of the Quillaja saponaria tree, resulting in a terminal harvest. While important advances have been made in harvesting the raw materials, there remain critical limits to the availability of trees and sustainability of raw material supply.

QS-21 is combined with the toll-like receptor (TLR) 4 agonist monophosphoryl lipid A (MPL) to create the AS01 adjuvant.

Clinical Experience

Saponin adjuvants have been studied in human clinical trials for decades in infectious disease and oncology applications. They are widely recognized as potent stimulators of the immune system; however, their development has been limited by a high level of adverse events after vaccination. Some saponin-adjuvanted vaccines are associated with more local (redness, swelling, and pain at the injection site) and systematic (fever, chills, and body aches) reactions than those with other adjuvants or non-adjuvanted vaccines.

Saponin adjuvants alone are critical components in vaccines in clinical development for COVID-19, flu and malaria, and the combination adjuvant AS01 is found in vaccines for herpes zoster, malaria, and tuberculosis.