The Tdap vaccine is a combination booster shot. It protects preteens and adults against three diseases: tetanus, diphtheria, and pertussis (or whooping cough).

Tetanus and diphtheria are rare in the United States today, but whooping cough continues to spread.

The Tdap vaccine became available in 2005 for older children and adults. Before 2005, there was no pertussis booster shot for anybody over 6 years of age.

Young children have been vaccinated against whooping cough since the 1940s. But protection against the disease naturally wears off over time.

Tdap protects adults from whooping cough, which can be debilitating and last for months. It also helps to protect infants who are too young to be vaccinated against whooping cough and could catch the disease from adults around them. Parents, siblings, and grandparents are often the source of whooping cough in infants.

Tdap is different than the DTaP vaccine, which is given to infants and children in five doses, starting at 2 months of age.

The Centers for Disease Control and Prevention (CDC) recommends that adults get a dose of Tdap in place of their next Td (tetanus-diphtheria) booster if:

  • You’ve never gotten the Tdap shot.
  • You don’t remember if you’ve ever had the Tdap shot.

A Td booster is usually given every 10 years with a single injection in the upper arm.

You should get a Tdap booster before the 10-year interval if:

  • You anticipate having close contact with an infant younger than 12 months. Ideally, you should get the shot at least two weeks before holding the new baby.
  • You’re pregnant. Pregnant women should get a Tdap booster with every pregnancy.

You shouldn’t get a Tdap booster if:

  • You have had a previous life-threatening allergic reaction to any vaccine containing tetanus, diphtheria, or pertussis.
  • You had coma or seizures within seven days of a childhood dose of DTP or DTaP, or a previous dose of Tdap.

Talk to your doctor if you have seizures or another condition that affects the nervous system. Also, let your doctor know if you’ve ever had Guillain-Barré syndrome or if you’ve ever experienced severe pain or swelling after any previous vaccine containing diphtheria, tetanus, or pertussis.

Every vaccine comes with a chance of side effects, and the Tdap vaccine is no exception. Fortunately, reported side effects with Tdap are generally mild and go away on their own.

Mild to moderate side effects may include:

  • mild pain, redness, or swelling at the shot site
  • tiredness
  • body aches
  • headache
  • nausea, vomiting, or diarrhea
  • fever
  • swelling of the entire arm in which the vaccine was given

Severe problems after the Tdap vaccine are rarely reported, but may include:

  • Severe swelling, pain, or bleeding in the arm where the shot was given.
  • A very high fever.
  • Signs of allergic reaction within a few minutes to a few hours of vaccine. These may include: hives, swelling of the face or throat, difficulty breathing, rapid heartbeat, and dizziness.

Allergic reactions from vaccines are very rare. The CDC estimates that fewer than one in a million doses of the vaccine result in an allergic reaction.