Limited and Decreasing Supply
Quillaja bark is only extracted from very mature trees and employed for multiple purposes. Bark exports are decreasing and the price of bark increasing every year because of national regulations limiting the volume.
Supply of QS-21 purified from bark is estimated to be limited to 6 million doses. Conventional sourcing based on Quillaja bark and manufacturing processes produce very limited amount of Quillaja–based adjuvants limiting the development and sustainability of vaccines.
Several saponin materials commercially available, are still reliant on unsecure quillaja bark supply.
