I have had the flu only once and you would DEFINATLY know it if you have ever had it. It would certainly not be mistaken for a cold or sniffle! It is the worst feeling I have ever had!
As for the trials, people do trials all the time and come out all right. I however, would not partake. If I am to get sick it would be of natural cause! That is just me though.
I am uncertain about the A strand, but you could google and find out more info or talk to your doctor for some accurate medical advice.
I do get a flu shot about once a year. They say that is will make you a little sick. Sometimes after the shot I feel a little woosy that is about it. My boyfriends 'medical' roomie told me last week that the flu shot is taken from the virus (for the states, I believe we are injected from South American flu season the year before and it just goes 'round the world) Yuk. I could only imagine the trials MAY make you feel a little down. THat is the first time I had heard about the flu shot in that way.
Outside my rambling (I am tired and sleepy!) I would obtain AS MUCH information as possible before I did any trials. You never know these days what the outcome would be. Plus, if you are relatively healthy you probably have a strong immune system that I wouldn't tamper with!
That is just my personal advice for you