The flu vaccine is usually update each year but we never hear any fuss that it is unsafe and has to be trialed for 8 years before it is safe. I thought I had had the flu a couple times and I had a good immune system so no worries.I can tell you when you get the flu you will know and will line up the next year for the flu vaccine unless you want a few weeks feeling like shite ,aching all over and long drawn out headaches.
