Incomplete Freund's Adjuvant (IFA) is a water-in-oil emulsion that is similar to the Complete Freund's Adjuvant (CFA) without addition of heat-killed mycobacteria (Mycobacterum butyricum). IFA and CFA are among the most used adjuvants and have been used extensively in experimental immunology. IFA has been used for decades in practical veterinary vaccination.
IFAVax consists of a mixture of mineral oil and emulsifier in a ratio of 85% v/v oil and 15% v/v emulsifier. Importantly, the IFAVax is not a pre-formed emulsion and thus it must be mixed with an equal volume of aqueous solution of antigen and subsequently emulsified prior to use.