No vaccine for NiV disease has been developed so far that would be both safe and protective for humans. The two vaccination strategies that have already been explored are the canary pox-based vector approach [26] and soluble subunit approach [28, 29] . NiV vaccine by the former method is undergoing development as a veterinary vaccine [26] . The same approach is being evaluated for human use vaccines, mainly for the prevention of HIV and AIDS [27] . The subunit approach has limitations as already mentioned above [28, 29, 30, 31, 32] . One particular challenge revealed by studies that tested a soluble NiV G protein-based subunit vaccine formulated with adjuvant is the potential difficulty of eradicating infection in the central nervous system. In that study [28] , live virus was present in the brain of one cat, and viral RNA was present throughout the 21 day postchallenge period in the brains of the remaining challenged animals. A recently reported vaccination strategy [34] requires simultaneous inoculation of two VSVDG vectors, one expressing NiV G, and the other expressing NiV F proteins. It was of interest to note that supernatants of cells co-infected with these two defective viruses were infectious and could be passaged indefinitely in the absence of VSV G trans-complementation. This vaccination approach seems promising since self-propagated stock of these two viruses induced robust neutralizing antibody response in mice. However, potential pathogenicity of VSV-based vaccine vectors remains a concern [34, 35] . The potential of a recombination event resulting in a single VSV vector virus expressing both these NiV proteins is unlikely, but it may still be problematic for a human use vaccine.