Aluminum hydroxyphosphate sulfate (AAHS)

Aluminum hydroxyphosphate sulfate (AAHS) is a proprietary amorphous inorganic salt used as an adjuvant in several widely administered vaccines to enhance the magnitude and duration of the immune response. Unlike traditional aluminum hydroxide or phosphate, AAHS is specifically formulated to optimize the adsorption of complex antigens, such as the virus-like particles (VLPs) found in Human Papillomavirus (HPV) vaccines. Its primary mechanism involves the creation of a 'depot effect' at the injection site, which allows for the slow release of antigens and prolonged exposure to the immune system. Additionally, AAHS acts as an immunostimulant by triggering the NLRP3 inflammasome, leading to the recruitment and activation of antigen-presenting cells like dendritic cells and macrophages. While it is not a therapeutic target itself, it is a critical component in the prevention of infectious diseases including Hepatitis A, Hepatitis B, and HPV-related cancers. The safety profile of AAHS is well-established through extensive clinical use, with the most common side effects being transient local injection site reactions.

Other names

Amorphous aluminum hydroxyphosphate sulfateAAHSMerck aluminum adjuvantAluminum hydroxyphosphate sulfate adjuvant

Acts as a vaccine adjuvant by adsorbing antigens to its surface, creating a depot for slow antigen release, and stimulating the innate immune system through NLRP3 inflammasome activation and recruitment of antigen-presenting cells.