Studies on an AS04-adjuvanted HPV-16/18 vaccine showed a high and sustained immune response to HPV antigens after injection, including in patients receiving subsequent doses. Immune response was enhanced by the MPL component which triggered local NF-kB and cytokine production, leading to increased activation of antigen-presenting cells. Immune response duration was extended by the aluminium hydroxide component. The HPV-16/18 AS04-adjuvanted vaccine showed enhanced efficacy compared to an aluminium salt-adjuvanted formulation, with a higher level of antibodies subsequently detected in the body. 
Long-term studies appear to show an adequate efficacy and safety profile.