 It is a water-in-oil emulsion and consists of squalene, an emulsifier (sorbitan monooleate 80), a patented block copolymer and microparticulate silica (Stills 2005).Toxicity seems to be lower than other water in oil adjuvant such as Freund's adjuvant.The efficacy to elicit an immune response against antigens of low immunogenicity is however subject to debate.