suggesting that a replication-competent PAV3 vector which would be easy to produce at high titres could also be a promising vaccine candidate. Nevertheless, performance of this new vaccine vector will need to be addressed in other animal species, including nonhuman primates, before its real utility as a human vaccine can be predicted more accurately. Overall, this study supports a complementary role for cellular immunity during early H5N1 infection and the further development of porcine adenoviruses as human vaccine candidates.