Tetanus: no vaccine trial ?

[Fièvre]

On this official site ( http://www.cdc.gov/vaccines/pubs/pinkbook/downloads/tetanus.pdf ) one can read :
Efficacy of the toxoid has never been studied in a vaccine trial.I am not sure to fully understand this : since tetanus related disease is reputed fatal how could vaccine trials be possible ? Would ethics authorized to deliberatly wound peoples so as to compare between vaccinated and not vaccinated people ?

[Momtezuma Tuatara]

Polio can also be fatal, and they had trials for that vaccine.

They didn't give the polio vaccinated and unvaccinated "polio" to see if the vaccine worked, so why would they deliberately wound anyone to see if a tetanus vaccine worked?

The major problem with tetanus is, that if you look at history of tetanus, though the rates vary a bit from country to country, New Zealand's prevaccine rate of 1.1 case per 100,000 people per year, is about right. So you'd have to do such a huge trial of the vaccine over a very long time, in order to see if the vaccine worked, so in the case of tetanus, you'd have to do a retrospective trial by tracking those who had the vaccine, and comparing them with those who didn't.

Which they have never bothered doing.