1. Macrophages are important in surviving influenza infection mainly due to their role as APCs. Macrophages are not the only APCs that can initiate an immune response against influenza. There are also dendritic cells and B cells that do the same thing.
2. There is currently only one serotype of chickenpox virus circulating in humans. Infection results in immunity to the only virus that is out there. In addition, you come in contact with chickenpox on a fairly regular basis just by interacting with others. These secondary exposures continually boost your immunity, and so it is life-long.
Influenza viruses, on the other hand, mutate rapidly from year to year. Infection with influenza this year may or may not protect you against next year's virus. It just depends on how much the virus changes during that season. This is not predictable, but must be continually monitored.
Just stuff I know.