If your son's vaccines are up to date, then I don't think he would have to have a tetanus booster. Either way, I wouldn't have him get it. I did a lot of research on the DTP booster a couple of years back when one of mine kids were "due" for it for high school. The boosters still contain thimerasol among many other horrible things. Everyone gave me much grief in trying to find out how to get around giving her the shot. I finally ended up with a religious exemption (after more grief from the health dept.)

My other daughter is now getting ready for college and I received a letter from the school that was worded in such a way that it sounded like she had to have the menengitis and something else shots. I checked the state requirements, and found that the law was that they had to inform her of the "dangers" of the disease and the availibility of the vaccine, but NOT that she HAD to have the vaccine. They are very tricky in their wording!
It's hard work, but worth it to save them from additional toxins.

Good luck