Comment Re:...what's the point? (Score 1) 156
Influenza is and has always been lethal. There are different types of influenzavirus A, and they are named based on the two main proteins that allow it to infect cells: hemagglutinin (H) and neuraminidase (N). A new strain can result from mutation after an influenza virus is transmitted from an animal species to humans. My understanding is that (small) viral mutations occur all the time; thus, we create a flu vaccine based on the three strains that we believe are going to be most common in the next year. These are the seasonal epidemics, and are caused by antigenic drift. The "old" strains will either have died out or many people will still have immunity to them. However, if a gene reassortment occurs involving strains from different animal species (antigenic shift), then a global pandemic can result. The pandemic ends after people begin developing immunity to the new strain, and new infections begin to drop, and this phase is called the post-pandemic phase.
(In response to your other post...) incidentally, I have narcolepsy, although it wasn't caused by the vaccine. I wonder how the vaccine may have lead to these cases, though.