Karen

>>First, do you remember what it was about horses? This kind of surprised
me. I thought it was grime and dirt in general. I don't immunize my
children but I DO live in an area with horses freely roaming the streets. <<

This is from a tetanus info site:
Tetanus, also sometimes called "lockjaw", is caused by a toxin produced by a
bacteria called Clostridium tetani. C. tetani is found all over, including
soil (the garden and field kind), stool and manure, and anything lying on
the ground. Rusty metal is also a favourite place for C. tetani to hang out,
and in fact puncture wounds with rusty nails are a common cause of tetanus.
C. tetani grows in wounds, especially closed wounds like punctures, and
produces a toxin that paralyzes muscles -- thus the term "lockjaw". In the
worst case tetanus can kill by paralyzing the breathing muscles. Although C.
tetani itself can be treated easily with penicillin, antibiotics will not
destroy or neutralize the toxin. Antibodies to the toxin can bind to and
inactivate the toxin before it attacks muscles and nerves

As far as the vaccines derived from human cell lines, this explains it as
well as I've seen it anywhere: http://www.cogforlife.org/vaxbrochsample.htm