Not fully studied yet, but this is something else to consider when thinking about getting flu shots.
http://uk.reuters.com/article/idUKTRE58O5ZG20090925
Although I wasn't tested, I think I came down with a case of swine flu this summer. It had me out of work for about a week, and had problems doing short walks/hikes for a little over a month after that because of the problems with my lungs. My wife is following this one pretty closely, sounds like those in charge are scared, so be careful this year.