Influenza viruses infect a wide range of animal hosts and cause yearly wintertime epidemics among people living in temperate zones. Because of their ability to mutate, re-assort gene segments, and cross species, influenza viruses can also lead to pandemics in which immunologically naïve people are exposed to a new, highly contagious subtype. In the last century, these pandemics were caused by influenza viruses whose surface attachment proteins, or hemagglutinins, were derived from birds, the natural reservoir of influenza virus. Vaccines are the primary means to provide protection for people at risk for inter-pandemic influenza, and new vaccines, directed against avian-potentially pandemic-strains are now being tested. To date, these vaccines have been shown to be safe and well tolerated, but have required multiple doses and dosage levels higher than traditionally needed for seasonal influenza vaccines in order to generate immune responses thought to be protective. No efficacy studies have yet been performed. Future efforts will be directed toward adjuvants, different routes of administration, newer manufacturing methods, and possibly new viral targets.