You can get the tetanus shot after the fact. Four is a low enough number to account for people who are completely stupid/lazy/indifferent, and some whom for whatever reason (health or religion) cannot get the shot.
Four cases (NOT deaths) in children in one year is nothing compared to the number of children who die from five gallon buckets, for instance.
We do not need a universal law to get the number four down to two.
Stepped on a rusty roofing nail and went to The Shot Nurse that day. Insurance covered 100% of the cost.