as04 as04 adjuvant system 04 or as04 is a trade name for combination of adjuvants used in various vaccine products by glaxosmithkline, in particular the fendrix hepatitis b vaccine. it is also one of the ingredients of the human papillomavirus vaccine (hpv). studies of as04-adjuvanted hpv vaccine showed high and justified immune response against to hpv antigens. furthermore, patients who took hpv-16/18 as04-adjuvanted vaccine previously showed strong rapid responses upon receiving subsequent doses. it consists of aluminum hydroxide and monophosphoryl lipid a (mpl). furthermore, it is the successor of as03 which is a squalene based adjuvant approved for pandemic vaccine by the ema. the heightened immune response was caused by the mpl component in as04 which increased nf-kb and cytokine production. the aluminum hydroxide component in as04 made the response last for a longer period of time. this is the reason why the hpv-16/18 as04-adjuvanted vaccine was shown to be more efficient compared to an aluminum salt-adjuvanted formulation with a higher level of antibodies found in the body.