What is your opinion of the Swine Flu Jab for under 5's?

My little boy (who is nearly 4) has had a letter saying that this is now available to him. I'm not sure what to do, so many people are against it, but on the other hand I know loads of people who have had swine flu and I really wouldn't want my little man to go through that!! Other peoples opinions would be grarefully received!