The most common side effect of a tetanus shot is soreness at the injection site, which typically starts within hours and resolves on its own within a few days. Most people experience only mild reactions, and serious side effects are rare. Here’s what to expect and what to watch for.
Common Side Effects
Pain, redness, and swelling where the needle went in are by far the most frequent reactions. These injection site symptoms show up within the first day and generally fade within two to three days. A small number of people also develop a low-grade fever.
Some people feel generally tired or achy for a day or two after the shot. These whole-body symptoms are signs your immune system is responding to the vaccine, not signs of illness. They’re mild enough that most people go about their normal routine.
Tdap vs. Td: Which Causes More Reactions
Tetanus vaccines come in a few forms. The version most adults receive is either Tdap (which also covers diphtheria and whooping cough) or Td (diphtheria and tetanus only). Children under seven typically get DTaP, which contains higher amounts of the active ingredients.
Tdap was specifically designed with lower amounts of diphtheria and pertussis proteins to reduce side effects in older children, teens, and adults. The older DTaP formulation caused noticeable arm swelling in some adults and adolescents, likely due to higher antibody responses to diphtheria. About 3 out of every 100 children experience limb swelling after the fourth or fifth dose of DTaP. The reformulated Tdap version is much less likely to cause this kind of reaction.
How to Manage Arm Soreness
If your arm is sore after the shot, over-the-counter pain relievers like acetaminophen (Tylenol) or ibuprofen (Advil, Motrin) can help. Applying ice or a cold pack to the sore area for 10 to 20 minutes at a time also reduces discomfort. Place a thin cloth between the ice and your skin. Avoid giving aspirin to anyone younger than 20, as it has been linked to a serious condition called Reye syndrome.
Moving your arm gently throughout the day can also help prevent stiffness. Most people find the soreness peaks on the first day and is largely gone by day three.
Rare but Serious Reactions
Severe allergic reactions to the tetanus vaccine are estimated to occur in roughly 1 in every 1 million doses. Symptoms of a serious allergic reaction include difficulty breathing, swelling of the face, lips, tongue, or throat, hives, and vomiting. These reactions typically happen within minutes to hours of the shot and require emergency medical attention.
Guillain-Barré syndrome, a condition where the immune system attacks the nerves and causes temporary weakness or paralysis, has been reported in rare cases following tetanus-containing vaccines. If you’ve had this condition within six weeks of a previous tetanus shot, that’s considered a reason to avoid further doses until you’ve discussed it with a provider.
Another uncommon reaction is called an Arthus-type hypersensitivity response, which involves severe swelling, pain, and sometimes skin breakdown at the injection site. This tends to happen in people who’ve received tetanus boosters too frequently. If you’ve had this type of reaction before, guidelines recommend waiting at least 10 years before your next tetanus-containing vaccine.
Who Should Be Cautious
A few situations call for extra consideration before getting a tetanus shot:
- Previous severe allergic reaction to a tetanus vaccine or any of its components. This is the clearest reason to avoid further doses.
- History of Guillain-Barré syndrome within six weeks of a prior tetanus-containing vaccine.
- Neurological conditions in children. For DTaP specifically, progressive neurological disorders like uncontrolled epilepsy may be a reason to delay vaccination until the condition is stabilized.
- Encephalopathy (severe brain dysfunction including seizures or decreased consciousness) within seven days of a previous dose, when no other cause was identified.
Having a moderate or severe illness at the time of your appointment is generally a reason to postpone the shot until you’ve recovered, though a mild cold or low-grade fever isn’t a concern.
What the Safety Data Shows
An analysis of over 57,000 children under age seven in the U.S. adverse event reporting system, covering reports from 1990 through May 2025, found that the most commonly flagged non-serious events after DTaP were injection site redness and swelling. Among serious events, fever was the most frequently reported, followed by seizures and vomiting. The vast majority of reported reactions were mild and self-limiting.
Outside of extremely rare allergic reactions, no serious adverse events have been shown to be caused by Tdap vaccination in the adult and adolescent population. The tetanus vaccine has been in use for decades and has one of the most well-established safety profiles of any routine immunization.