This is the first time a trivalent cold-adapted intranasal flu vaccine has been tested in such a large U.S. field trial. Background on Influenza Influenza, an acute respiratory infection, is caused by a variety of flu viruses. The viruses spread from person to person via airborne droplets of respiratory fluids, especially after an infected individual sneezes or coughs. Flu viruses generally enter the body through the mucous membranes of the eyes, nose or mouth. Prominent symptoms include headache, chills and a dry cough, which are followed rapidly by body aches, malaise and fever.
Most people recover from the flu within a week.
However, for those at high risk, such as the elderly and people with certain chronic illnesses, flu and its complications can be life-threatening. Complications such as pneumonia generally result from secondary bacterial infections in the lower respiratory tract. In addition, a neurologic disease known as Reye's syndrome sometimes develops in a small number of children and adolescents who are recovering from flu. The syndrome is associated with the use of aspirin, which often is contained in medications for relieving the pain or fever of flu. Outbreaks of flu usually begin abruptly.