This may be a silly question but I just wondered, if Pandemrix is made in the same way as the seasonal flu vaccine why does one give you a very sore arm and the other doesn't. I've read lots of accounts of people having both and commenting on the sore arm from the SF jab. What ingredient causes the sore arm reaction(thiomersal?)? Is it not in the season flu vaccine? I can find the ingredients for Pandemrix but cannot find any ingredients for Seasonal flu vaccine, if anyone can link would be grateful.