I received a tetanus booster shot in the Urgent Care department while waiting to get my finger stitched up after mistaking it for an onion. I happened to know that it had been about ten years (time flies) since my last one because I was just planning to get an update. I wondered how a booster shot worked and why I needed one. Remember that I'm no medical doctor and you shouldn't rely on the internet instead of seeing one.
At issue is the presence of a bacterium called Clostridium tetani. Its nearly invincible spore form can be commonly found in soil. The stereotypical scenario for the spore to enter your body is stepping on a rusty nail, but really, any open wound will do. This is one of the reasons when you get any sort of cut, you're supposed to clean it well.
The temperature and lack of oxygen found in injured tissues can be just right for C. tetani to transform into its vegetative self capable of producing tetanospasmin, a toxin second only to botulinus for potency. The tetanus toxin attacks the central nervous system, resulting in extreme rigidity and spasms. Tetanus is also called lockjaw because an early symptom of an attack includes spasming of jaw muscles. Small amounts of bacteria can produce enough toxin to shut down your heart and respiratory system before your immune system can detect and react to them. This is why a vaccine is so important.
The tetanus vaccine contains tetanus toxoid, which is chemically sterilized tetanus toxin that stimulates your immune system to produce antigens able to attack and dismantle active tetanus toxin. In British Columbia, beginning in infancy, children usually receive a series of shots that include other vaccines as well.
Unlike many of the illnesses for which vaccines are given, tetanus does not spread from other people. Tetanus is rare in places where immunization is widespread, but your risk of exposure remains the same, no matter how many people get vaccinated. If you choose not to protect yourself, at least you are only endangering yourself. It's probably better to keep track of your booster shots so you're up-to-date rather than waiting until you have an injury, like I did. You might get tetanus but not have access to the vaccine. Victims tend to be unimmunized or have not had a booster within ten years. Of those who get tetanus, about 1 in 5 will die.
People vary in their response to the vaccine, but generally your body's preparedness to tetanus decreases over time. Ten years is a conservative estimate for when you should get an update. Getting it sooner is not considered a problem.
If you have any gory stories about when you made sure you had a tetanus shot, share them in the comments.