eli5- why do you get a tetanus shot even after you cut yourself with something rusty?

Question

If shots (vaccines) are supposed to simulate the infection before getting the real thing, why does it work after you get the actual virus in your body

In: 1

Answer 1

There’s only a few microbes in you initially. The shot helps you build immunity before the infection progresses too far.

However, tetanus bacteria is anaerobic. So for an advanced infection, they excise tissue all around the initial wound and the exposure to air kills the tetanus. This may be related to the old wives tale that wounds need to breathe to heal: a wound that would have given you what was once lethal tetanus wouldn’t if it got air.