No matter the design of DNA vaccines that may be used, recent studies have indicated that DNA priming immunization is effective as part of the prime -boost strategy for flu vaccine applications. In addition to DNA prime-inactivated flu vaccine boost [9, 10] , a study published in 2011 further demonstrated that DNA primelive attenuated flu vaccine boost was equal to or more effective than twice immunization with the live attenuated flu vaccine against the H5N1 viruses based on antibody responses and viral clearance in immunized ferrets [42] . Since live attenuated vaccines are considered the most immunogenic form of vaccines, it is impressive to observe that one time DNA prime was able to achieve the same priming effect as a live attenuated flu vaccine. In this particular study, the H5-VN.tPA DNA insert was used as part of the collaboration with the manufacturer of live attenuated H5N1 flu vaccine.