Summer brings opportunities for gardening, which is supposed to be a way to relax. But encountering a thorn, splinter, or the legendary rusty nail can often stir questions about tetanus, a disease caused by a bacterial toxin that can result in paralysis and even death. We’re vaccinated against tetanus early in life, but if you happen to suffer a puncture wound near soil, you could be wondering how long those injections are good for and how often you need a booster shot. Take a look at some common questions about tetanus and learn the best way to proceed the next time you feel a sharp poke in your hands or feet.

1. What is tetanus?

Tetanus is the name of a disease caused by the toxin of the Clostridium tetani bacterium. The disease attacks the central nervous system, causing stiffened muscles, increased heart rate, and fever. The muscle spasms can be severe, leading to broken bones, vocal cord issues, and breathing problems. A tightening of the facial muscles gives tetanus the informal name of “lockjaw.” Symptoms usually appear between three and 21 days following exposure. Due to breathing problems caused by the stiffened muscles, one to two people out of every 10 will die as a result of the infection. But because of the effectiveness of the vaccine, the United States sees only about 50 cases of tetanus each year.

2. How do people get tetanus?

People contract tetanus when the bacteria enters the body in an open wound. Because the bacteria is typically found in soil or manure, puncture wounds as a result of landscaping can be of particular concern, though these “dirty wounds” can also be a result of any injury involving soil, feces, or saliva, like a human or animal bite.

3. Aren’t people vaccinated against tetanus as infants?

Yes. Infants receive a total of four DTaP shots at 2, 4, and 6 months of age, and again between 15 and 18 months. A fifth shot is given when the child is between 4 and 6 years old. DTaP is a combination vaccine that protects against tetanus as well as diphtheria—an infection that attacks the mucus membranes of the nose and throat—and pertussis (whooping cough). An additional booster shot for all three (called Tdap) is given at 11 to 12 years of age.

4. Why would anyone need a tetanus booster shot?

Tetanus vaccines do not last for a lifetime. The Centers for Disease Control and Prevention recommends that adults receive a tetanus booster (Td) every 10 years. (Pregnant women should get Tdap in their third trimester to help boost a baby’s resistance to whooping cough.) If they did not get Tdap as a preteen, they should have that instead. The booster can be given at any time and is typically administered even if an adult doesn’t remember or their health records don’t indicate the last time they received a shot. Virtually everyone who receives the shot will be protected against tetanus for the subsequent decade. Roughly 95 out of 100 people will be protected against diphtheria. Roughly 98 out of 100 children will be resistant to whooping cough within a year of receiving their last dose, or seven in 10 if the dose was given within the last five years. Overall, Tdap protects against whooping cough in seven out of 10 people in the first year, and three to four out of 10 people within four years.

In 2016, a study in the journal Clinical Infectious Diseases [PDF] suggested that immunity might actually last as long as 30 years for tetanus and diphtheria. The CDC, however, has not yet altered its guidelines for vaccinations.

5. Should I get a tetanus booster shot if I get a puncture wound even if I just had a shot a few years ago?

If you have had a documented booster shot within the past five years and suffer a puncture wound, your physician won’t likely recommend another. If it’s been more than five years, you will probably receive a booster as a precaution. If your vaccination status is unclear, your doctor will administer a primary series of three doses. You might also be given TIG, a shot which provides temporary immunity and an antitoxin.

6. What should I do if I suffer a puncture wound?

If you are injured with an object from an area that could potentially harbor Clostridium tetani, wash the affected body part thoroughly and contact your physician to see if your tetanus vaccinations are up to date. If it’s been more than five years or your status is unclear, you’ll be given a booster.