Tetanus can cause painful muscle spasms so severe it has been called the “grinning death” because, if not treated, it can lock the jaw shut and pull the face into a potentially life-threatening, agonizing smile. But despite symptoms that sound like something out of a horror movie, this isn’t a disease most people think about very often.
One reason is that it’s rare. There are typically fewer than 40 cases each year in the United States, down from around 500 to 600 annually before the tetanus toxoid-containing vaccine (TTCV) became available in 1924, according to the Centers for Disease Control and Prevention.
But despite being entirely preventable, tetanus hasn’t disappeared. Tetanus cases are on the rise, a recent JAMA viewpoint noted: Thirty-eight U.S. cases were reported in 2025, the most in a single year since 2006. Tetanus continues to occur in the unvaccinated, partially vaccinated or those who have skipped their 10-year booster doses. In April, the CDC released findings from an investigation into four unvaccinated children who developed tetanus in 2024; all four were hospitalized eight to 45 days, and survived with tetanus immunoglobulin treatment after their symptoms started.
Because the vaccine has been so successful, most people alive today have never known anyone with tetanus, noted William Schaffner, a professor of infectious diseases at the Vanderbilt University Medical Center, but “it’s a very, very serious illness,” he said. Early symptoms like lockjaw can lead to serious complications, such as a pulmonary embolism or difficulty breathing. One in 10 tetanus cases are fatal.
Experts fear lower vaccination rates may allow tetanus to become more common. In the CDC’s findings on vaccination coverage and exemptions among kindergartners for the 2024-2025 school year, coverage for all reported vaccines declined, including DTaP, the combined childhood vaccine that protects against tetanus as well as diphtheria and pertussis. “If we don’t vaccinate, these diseases of yesteryear will return,” said Schaffner.
What causes tetanus?
Unlike most vaccine-preventable diseases, tetanus is not spread person-to-person. Infections are caused by a bacterium called Clostridium tetani (C. tetani), which exists in soil, manure and dust all around the world. When C. tetani spores enter the body through broken skin, they produce an illness-causing tetanus toxin.
When you hear tetanus, you probably think about stepping on a rusty nail. But there are countless other ways a person might get infected. “Any wound that is contaminated with dirt is at risk of introducing tetanus bacteria into your body,” said Paul Offit, director of the Vaccine Education Center and an attending physician in the Division of Infectious Diseases at Children’s Hospital of Philadelphia. That includes puncture wounds and dead tissue injuries such as burns or frostbite, as well as, less commonly, sores, insect bites or smaller breaks in the skin.
The children in the CDC’s recent report sustained a range of injuries that led to tetanus, including one from an ankle fracture and another that occurred when a horse stepped on the child’s foot.
Schaffner recalled a patient who developed tetanus after accidentally cutting themselves with a kitchen knife. “Where that person contaminated that very clean wound, nobody ever knew,” he said. “But the tetanus bacteria is out there everywhere, and it will never go away.”
Why is tetanus so dangerous?
Tetanus doesn’t initially present as redness, swelling or a fever, symptoms typical of most other wound infections, said Schaffner. Instead, C. tetani releases the tetanus toxin tetanospasmin, a single-chain protein that circulates throughout the body and eventually impacts the nervous system. “When it gets to the brain, it causes an illness characterized by lockjaw,” he said.
It can take anywhere from three to 21 days after C. tetani exposure before a person develops symptoms, and these muscle spasms in the jaw are often one of the first signs of tetanus infection. Other early symptoms may include difficulty swallowing, headache, muscle stiffness and other sudden muscle spasms in different parts of the body. Even the slightest sensory disturbance, like exposure to sound or light, can trigger these spasms, said Offit. “It’s very hard to watch.”
One type of muscle spasm, risus sardonicus, can cause a person’s facial muscles to involuntarily contract, so “it looks like they’re smiling, but they’re not,” said Walter Orenstein, professor emeritus in the Division of Infectious Diseases at the Emory University School of Medicine. Another, called opisthotonos, makes muscles in the neck, back and legs dramatically arch backward into a C-shape position.
Tetanus-related muscle spasms can be severe enough to fracture bones, make breathing difficult and become life-threatening.
Adding to the risk, unvaccinated people don’t benefit from any kind of herd immunity with tetanus, nor does a prior infection offer protection.
If a person gets measles and recovers, for example, the immune system develops antibodies to prevent reinfection — but that’s not the case with tetanus, said Schaffner, because the amount of tetanospasmin that causes tetanus infection is so small, the immune system doesn’t learn to recognize it. “Even people who’ve experienced this horrific illness still have to be vaccinated in order to prevent another infection sometime later in life,” he said.
How can you protect yourself and loved ones from tetanus?
Tetanus is highly preventable, thanks to “a brilliantly effective” vaccine, said Schaffner. Unlike tetanus infection, the vaccine contains an altered form of tetanospasmin to prime the immune system to destroy tetanospasmin before it affects the nerves, explained Orenstein. “It can’t cause disease, but it can induce a protective immune response,” he said.
Tetanus vaccination is recommended at different life stages: The DTaP vaccine is given as a three-shot series at 2 months, 4 months and 6 months, then as two boosters between 15 to 18 months and 4 to 6 years; the Tdap vaccine provides additional protection against tetanus, diphtheria and pertussis for preteens between 11 and 12 years old; and adults should receive the tetanus booster Td (for tetanus and diphtheria) every 10 years.
“To remain optimally protected, you need an initial three-dose series and then boosters every 10 years or so throughout your life, because your protection can wane,” said Schaffner.
Some people may also be advised to get a Tdap booster later in life, such as pregnant women, because this vaccine provides protection against pertussis for newborns, as well as adults who didn’t receive Tdap previously.
Not sure when your last Td booster was? If you get a wound that your doctor suspects may have exposed you to C. tetani and you can’t recall the timing of your most recent tetanus shot or believe your last one was more than five years ago, you’ll likely be given a Td booster as part of your wound care, said Schaffner.
And if you or your child haven’t received their full TTCV series, experts stressed it’s not too late to talk to your doctor about getting caught up.
“Vaccines, in a sense, are victims of their own success, because people aren’t seeing these diseases, so they don’t realize they’re getting any benefits,” said Orenstein. But the C. tetani bacterium will always be present in the environment, and tetanus cases can spike anytime vaccination coverage drops.
“My fear is, if we see fewer and fewer people getting vaccinated, we will see more and more cases of tetanus,” said Orenstein. “That concerns me.”
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