I can tell you from research that the Gulf War soldiers received many vaccines at once containing thimerosol (mercury). As a result they are comming up sick with MS and other strange illness. Basically, they have mercury poisoning.
Supposedly most of the vaccines are mercury free now, but I can tell you that some of them still contain it such as the Anthrax, Yellow fever, the flu shot. If you check the FDA website it will tell you which ones have it and which ones don't. This means your son did get some mercury, the question is how much. Probably less that the Gulf War Vets.
But none the less...whose to say how much is safe for anyone. And he very likely had mercury in his childhood vaccines. Mercury is cumulative. It just keeps adding more. Does he have metal fillings? If so, it might be worth looking into how much mercury load he has. Not to scare you or him or anything. He may feel fine now. Should he not feel well later on..you'll know where to look.