Interesting comment about the tetanus. I feel a mini-lecture coming on!
There was a time that people were advised to have boosters every ten years or so but then the microbiologists discovered that care workers who were seemingly non-responders after Hep B immunisation actually got a good register if they had an exposure to body fluids such as in needle stick injuries. At the time, any non-responder care-worker suffering a NS injury would be given a very painful, risky and expensive injection of live vaccine to protect them.
Looking into this further, they found that supposed non-responders actually did have immunity but it would only become recordable after exposure. So they began looking into other vaccines and found it was the same pretty much across the board. And this included tetanus. So the policy now (in the UK, don't know about elsewhere) is that once you've had the basic course you only need to have a booster if you've had an exposure. The regular boosters are no longer given.
Plus which, they also found that people often forgot to get their ten year boosters anyway yet still appeared to be covered in the event of any accident. And research confirmed the findings recording in the HepB scenario.
Sorry, can't quote any sources, this is from my own experience in Occupational Health in 94-96.