Questions & Answers
Diphtheria - The Vaccine
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  1. Is there a treatment for diphtheria?
    Diphtheria is treated with both antibiotics and with diphtheria antitoxin. Antitoxin is the name for antibodies that neutralize toxins. Diphtheria antitoxin is produced in horses and was first used in the United States in 1891. Antitoxin is not effective against toxin that is already attached to the body's tissues, but antitoxin will neutralize circulating poison and prevent the disease from getting worse. The patient should be tested for antitoxin sensitivity (because it is horse-derived) before administration.

  2. What kind of vaccine prevents diphtheria?
    The diphtheria vaccine consists of a modified toxin called a toxoid. The vaccine is made by growing the bacteria in a liquid medium and purifying and inactivating the toxin.

  3. When did the diphtheria vaccine become available?

    The first toxoid against diphtheria was developed around 1921, but was not widely used until the 1930’s. In the 1940’s, diphtheria was combined with pertussis vaccine and tetanus toxoid to make the combination DTP (or DTaP) vaccine for children.

    Diphtheria toxoid (DT) is also combined in other vaccines:

    • DT vaccine for the few children who cannot receive pertussis vaccine.
    • Td vaccine for people 7 years or older (tetanus toxoid and a reduced dose of diphtheria toxoid).
    • Tdap vaccine for people 10 years or older (tetanus toxoid with reduced doses of diphtheria toxoid and acellular pertussis vaccine).
    • Diphtheria toxoid is not available as a single vaccine.

  4. Who recommends this vaccine?
    The Centers for Disease Control and Prevention (CDC), the American Academy of Pediatrics (AAP), and the American Academy of Family Physicians (AAFP) all recommend this vaccine.

  5. How safe is this vaccine?
    Serious reactions after immunization are rare. The most common reactions are soreness, redness, and swelling at the injection site. Other possible reactions may include fussiness, mild fever, loss of appetite, tiredness, and vomiting. The use of the more purified DTaP vaccine, instead of DTP has decreased even these mild reactions.

  6. Can the vaccine cause diphtheria?

  7. Do I need to be immunized if I had diphtheria?
    Yes. Unfortunately, some people who suffer diphtheria illness do not produce enough antitoxin to prevent future illness. It is recommended that people recovering from diphtheria be immunized.

  8. What's the difference between DT and Td vaccines?
    The difference is the amount of diphtheria toxoid contained in each dose. Pediatric DT ("big D") contains 3 to 5 times more diphtheria toxoid than the adult Td ("little d"). DT is used for the few children who cannot receive the pertussis component of the DTaP vaccine, and Td is used for adults and children seven years of age and older who need booster doses of diphtheria and tetanus toxoid.

  9. Should adults who weren't immunized as children receive this vaccine as adults?
    Yes. Adults or children seven years and older without documentation of tetanus and diphtheria vaccination should receive a primary series of three doses of Tetanus-diphtheria toxoid (Td). The first two doses should be separated by 4 to 8 weeks, and the third dose given 6 to 12 months after the second dose. Td will protect you from diphtheria infection as well as tetanus.


  1. How is the vaccine given?
    The vaccine is given as a single injection into the muscle (IM). The usual schedule for infants is a series of four doses given at two, four, six, and 15 to 18 months of age. A fifth shot, or booster dose, is recommended at 4 to 6 years of age, unless the fourth dose was given late (after the fourth birthday). Because immunity to diphtheria and pertussis wanes with time, adolescents (11 to 18 years old) should receive a booster dose of Tdap and later booster doses of Td (adult tetanus and diphtheria) every ten years.

  2. I received Tdap a few days ago. Now my arm is red and swollen down to the elbow. What should I do?
    The redness and swelling may be an adverse event caused by your Tdap immunization. Contact your healthcare provider or the IHB. We can help you to get treatment and help you file a Vaccine Adverse Event Report.

  3. My child has a large lump where the DTaP shot was given. Should I take her to our pediatrician?
    DTaP vaccination may cause side effects, such as swelling, redness, pain, and/or warmth where the shot was given. These side effects may last for 1 to 2 days, and usually go away on their own. If you have more questions, contact a IHB healthcare provider and send us a photo of the reaction using our Ask VHC secure messaging.


  1. Who should NOT receive diphtheria vaccine?
    People who have had a serious allergic reaction to a dose of vaccine containing diphtheria toxoid should not receive another vaccination. Persons with a moderate or severe illness should postpone receiving the vaccine until their condition has improved.