how long does a tetanus shot last. My son has not had one...

Question: 

how long does a tetanus shot last. My son has not had one since high school, and he is 24 now

Answer: 

Adults who were immunized against tetanus and diphtheria when they were younger should get a booster dose of the tetanus and diphtheria (Td) vaccine every 10 years. This booster dose strengthens or boosts the immune system to give better protection against these diseases.

- Immunization Nurse