School-age children, however, are major carriers of the flu virus and thus help fuel epidemic spread of the illness. Children pass the virus among themselves at school, and then bring it home to their parents. The experimental vaccine is made from a live but weakened influenza virus that cannot cause the flu but stimulates anti-influenza antibodies in the respiratory tract. In prior clinical tests, the nose drop form of the vaccine has been shown to be safe and effective in children and adults. Influenza affects up to one-quarter of the U.S. population each year.
Epidemics usually occur from late fall to early spring.
About 30,000 people in the United States die from influenza and its complications each year. Those at highest risk include people ages 65 and older and people of any age who have chronic heart, lung, or kidney problems or who are residents of nursing homes. Current guidelines suggest that people in those risk groups receive an influenza vaccination each year. A more convenient vaccine that children and some adults may prefer to a needle injection could be used as part of a community-wide immunization program to reduce the hazard of epidemic influenza. This large multicenter trial includes two related protocols with a total target enrollment of 830 people.