As an adult who has never received a tetanus shot in my lifetime, would it be safe to get one now, or could there be adverse reactions?

Tetanus shot: By all means you should get a tetanus shot and to be sure you are properly immunized you should have three a month apart. The only side effect might be a sore arm for a day or two

Perfectly Safe: Yes! You should definitely get the vaccines! Since you have never had one you will need to have the three dose series to get your immune system up to speed. The first dose should be a Tdap (tetanus, diptheria, and pertussis), and the other two just a Td (tetanus and diptheria). The series is typically completed in 7 to 12 months. You should then get a TD booster every 10 years.

Tetanus: Tetanus is a disease causes by a bacteria called clostridium tetani. It is characterized by paralysis of the muscles including the diaphragm muscle which could be life threatening even leading to death. Tetanus can be easily prevented by taking a tetanus vaccine. The common side effects can be injection site reaction, pain and fever (with a combination vaccine), rarely an allergic reaction.