Influenza virus challenge.

<p>At week 5, mock vaccinated mice or mice vaccinated with vaccines (3 µg) were challenged intranasally with the mouse-adapted influenza ma-NC/99 virus (2.6×10⁵ pfu). Mice were monitored daily for weight loss, activity, and survival. Body weight is plotted as percentage of the average initial weight. Mice that lost greater than 20% body weight were sacrificed.