Tetanus is an infection caused by the bacterium Clostridium tetani. Tetanus infection (sometimes called lockjaw) can be extremely serious, causing involuntary muscle contractions and seizures.
However, thanks to highly effective vaccines, tetanus is rare in most developed countries. The complete vaccine series is nearly 100% effective for tetanus, according to the Centers for Disease Control and Prevention. And according to a health report from the Organisation for Economic Co-operation and Development, more than 90% of children in the United States, Canada, New Zealand and most of Europe receive shots that help to prevent this infection.
What is a tetanus shot?
Tetanus shots are vaccines. In the United States, they're usually administered together with the vaccines for diphtheria and pertussis (whooping cough). The most common names for these shots are DTaP, DTwP and Tdap. Each of these letters stands for one of the vaccines, while the "a" and "w" refer to the type of pertussis toxoid; either acellular or whole.
According to the World Health Organization, DTaP vaccines are usually given to children younger than age 7, while Tdap vaccines are given to adults and children over 7 years old. The main difference between these two vaccines is their concentration. The lowercase "d" and "p" in Tdap indicates that this vaccine has a lower level of diphtheria and pertussis toxoids.
Tetanus shots can also go by a few other names, like DT and Td. These vaccinations are tetanus shots that are administered with the vaccine for diphtheria and don't include pertussis toxoids.
Related: How do vaccines work?
The CDC recommends that children receive five doses of the DTaP vaccine by the time they're 6 years old and one more booster shot when they're 11 or 12 years old. The first three doses are usually given during the first year of life, with the first dose administered at 2 months old, second dose at 4 months old and third dose at 6 months old. The fourth DTaP dose is given to children at age 2, while the fifth and final dose is given between the ages of 4 and 6.
Experts also recommend a Tdap booster shot around age 12 and every 10 years thereafter. The CDC says that a Tdap booster is also recommended for pregnant people. Getting the booster between 27 and 36 weeks of pregnancy can provide the fetus with antibodies.
If DTaP vaccines aren't given on schedule, a doctor will likely recommend the Tdap shot instead. The lower concentration of diphtheria and pertussis toxoids in the Tdap shot provides protection while minimizing side effects in older children and adults.
What causes tetanus?
When most people think of tetanus, a rusty nail or fence is likely the first thing that comes to mind. This is a common misconception, though, as rust isn't the cause of tetanus infections. Rather, a type of bacteria called Clostridium tetani is the culprit, and it can be found in a variety of places, including soil, animal feces and even a knife from your kitchen.
Puncture wounds and deep, penetrating injuries are also often associated with tetanus. However, the Cleveland Clinic says that even minor wounds — like scrapes, scratches, splinters or insect bites — can allow C. tetani spores to enter the bloodstream, causing infection.
Outside, exposed to air, C. tetani spores are dormant. But as the bacteria travel through the bloodstream and away from oxygen, the spores begin to germinate and produce a potent toxin known as tetanospasmin, or tetanus toxin, according to the CDC. This potent toxin interferes with the release of neurotransmitters and blocks inhibitor signals, thus causing the quintessential tetanus symptoms such as seizures, uncontrolled muscle spasms and lockjaw.
Tetanus signs and symptoms
Tetanus symptoms usually begin around the original site of infection and affect the nerves in that area. If left untreated, tetanus will spread to other nerves and eventually to the spinal cord and brain. This is when symptoms can become particularly pronounced and life-threatening.
Symptoms vary and depend heavily on whether a person is vaccinated and kept up with booster shots. This, along with the location of the injury and its severity, will determine the exact course of treatment. People who didn't get fully vaccinated or didn't keep up with their boosters can expect more serious symptoms and will need more extensive treatment.
According to the CDC, there are three main types of tetanus:
1. Generalized tetanus, the most common type, causes death in 10% to 20% of people. This form of tetanus often starts out with a very recognizable "locked jaw" symptom. It progresses to increasingly serious issues, like painful muscle spasms, convulsions and seizures.
2. Localized tetanus is a mild, unusual form of this condition. It presents as muscle spasms close to the site of injury and often occurs in people with partial immunity. Sometimes, it can turn into generalized tetanus.
3. Cephalic tetanus, the rarest form of this condition, occurs after an injury to the face or head. This type of tetanus is accompanied by muscle weakness that occurs rapidly. It can also turn into generalized tetanus.
It takes about 10 days, on average, for the symptoms of tetanus to show up after an infection, according to the CDC. But the time between infection and symptoms can be as short as three days, so it's best to seek treatment as soon as possible if after an injury that may have led to C. tetani exposure.
Unlike with many other infections, antibiotics are not recommended as a treatment for tetanus. Instead, a tetanus booster shot is usually administered. "The general rule of thumb that we follow is that you get a tetanus shot not more than 48 hours after the injury,"said Dr. Jaydeep Tripathy, a primary care physician at Kamakshi Memorial Hospital, Chennai, India. "This is critical if the cause of the wound is dirty or infected, or if you have not had a tetanus shot in the last 10 years."
The Mayo Clinic and CDC also recommend this strategy. However, another dose of the vaccine may be unnecessary if the person received a booster shot or final dose of DTaP less than 5 years ago. It largely depends on the severity of the injury and how quickly medical care can be administered.
In some cases, such as when someone is in a remote location or is traveling, it may not be possible to get a tetanus shot in time. In these cases, the resulting infection can be very serious, especially if the person hasn't kept up with their booster shots. "The toxins can constrict your breathing and affect your entire respiratory system," Tripathy told Live Science. "Ultimately, you can die from the infection."
Certain people, like those who are immunocompromised, unvaccinated, not fully vaccinated or who have dirty or contaminated wounds may also require a different type of tetanus shot, called tetanus immune globulin (TIG). TIG is an antitoxin that can help remove unbound tetanus from the body. However, it can't remove any tetanus toxin that's already bound to nerves.
If you suspect a tetanus infection, it's best to talk to a doctor or seek medical attention as soon as possible, even if you can't get a shot right away. Tetanus is often treatable but may require medical interventions such as muscle relaxants and a ventilator, depending on the severity of the disease. If the infected person was unvaccinated or their vaccination status is unknown, the CDC also recommends starting the full series of DTaP or Tdap vaccines while administering any necessary treatments.
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Siddhi Camila Lama is an independent science, health and gastronomy writer who is also the managing editor of HairScience.org. She's written for Orb Media, Atlas Obscura, BrainFacts, Medium's science and tech publication, One Zero, and more. Siddhi is a certified nutritionist with a bachelor's in Human Development, a master's in Organ, Tissue, and Cellular Transplantation, and a Ph.D. in Bioengineering.