Animal influenza viruses, such as the H1N1 and H5N1 viruses, typically infect animals like birds or pigs, but these viruses can also infect humans. The recent outbreak of the H1N1 influenza virus demonstrates that it is possible for these viruses to cause a pandemic outbreak in humans. Researchers are specifically interested in evaluating vaccines for H2 viruses, as these viruses caused a pandemic outbreak in humans in the late 1950s to 1960s. In addition, over half of the world's current population has no previous exposure to related viruses, which means a pandemic outbreak could pose a serious health risk as many people would have no immunity against the virus. In 2006, an outbreak of H2N3 infection occurred in pigs in the Midwest United States. While no humans contracted the virus during that outbreak, it remains a concern for researchers in the event that the virus ever spreads to humans. The purpose of this study is to evaluate the safety and immunogenicity of two doses of an experimental H2N3 vaccine, H2N3 MO 2006/AA ca in healthy adults. This is a live attenuated vaccine, which means that participants will be exposed to small amounts of the H2N3 vaccine virus and will need to remain isolated for at least 12 days when receiving the vaccine to prevent spreading the virus to others.~This study will enroll healthy adults. Participants will receive two doses of the vaccine, 4 weeks apart, and will stay in an isolation facility during both 12-day vaccination periods. Participants will be admitted to the isolation facility 2 days before they receive their first vaccination. They will receive one nasal spray administration of the vaccine and will be monitored for side effects. On various days while in the isolation facility, they will undergo a physical exam, blood and urine collection, and a nasal wash procedure. Participants will remain in the isolation facility for at least 9 days after receiving the vaccine and possibly longer, until the nasal wash tests negative for the vaccine virus for 2 consecutive days. Participants will be readmitted to the isolation facility 26 days after the first vaccination. They will receive a second vaccination and all study procedures will be repeated. Participants will attend study visits 56, 82, and 208 days after the first vaccination for follow-up health and safety monitoring, blood collection, and a nasal wash procedure.
In recent years, influenza viruses that have traditionally infected animals have infected humans as well. The H2N3 influenza virus, which first appeared in pigs in the Midwest United States in 2006, may pose a potential health concern to humans. This study will evaluate the safety of and immune response to a vaccine designed to protect people from the H2N3 influenza virus.