I don't really understand it, either - but in the massive long FR thread about H1N1, steve86 has made interesting posting about the reported RE-infection. Here's an example:
H1N1 flu victim collapsed on way to hospital [Latest H1N1 updates downthread]
http://www.freerepublic.com/focus/f-news/2278371/posts
Post Number 5,039 of 5,368 steve86 to hennie pennie
>>> "Yes, I have had to revise my ideas about Influenza Type A re-infection and immunity.
It appears that any Type A has the ability to re-infect. This is because the immunity acquired through previous infection is not all or nothing — it is some degree of partial immunity, probably never perfect.
It does appear that when re-infection occurs with Type A seasonal flu the new infection is often asymptomatic.
Just as with natural influenza, the immunity conferred by a vaccination is partial. This is why flu shots don't always work — in addition to the problem of missing the dominant flu strain.
The question remains: why is the health establishment so adamantly pushing the H1N1 vaccine even to those who have already been infected — like my kids?
How on earth could the vaccine (dead virus) grant superior immunity to the actual live infection? This simply makes no sense, unless the vaccine includes genetic material that is anticipated to occur in the wild infection. Highly unlikely, IMO.
Guess I have a lot more to learn." <<<