An influenza pandemic could arise unexpectedly with rapid spread across the world. The efficiency of production of a vaccine and the ability to administer it widely will be among the most important factors in the ability to protect public health. The current process for producing inactivated or live attenuated influenza vaccines requires six to nine months. That reduces considerably the likelihood that the vaccine will be available during the first wave of the pandemic. Therefore, a key element of preparedness is to optimize the production process and to reduce the vaccine development time. During the 1997 H5N1 outbreak in Hong Kong, seed viruses were prepared for production of inactivated and live-attenuated vaccines. We used the cold-adapted A/Ann Arbor/6/60 as the donor virus to generate live attenuated vaccines containing genetically modified HA and NA genes from H5N1 influenza viruses. These reassortants were shown to be safe and protective in animal models. This study indicates that production of live attenuated avian influenza vaccines is feasible and that development of a library of reassortants containing different subtype HA and NA genes may reduce the vaccine preparation time for future influenza pandemics.