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Diphtheria, Tetanus, and Pertussis

What is Diphtheria?

Diphtheria is a disease caused by the bacterium Corynebacterium diphtheriae. Diphtheria used to be a leading cause of death among children in the US, but vaccination has made diphtheria very rare. Common symptoms include fever, sore throat, and a swollen neck. Diphtheria is a very dangerous disease that can cause difficulty breathing, heart failure, and paralysis. The vaccine is approximately 97% effective at preventing diphtheria infection. 

What is Tetanus?

Tetanus is a bacterial disease caused by Clostridium tetani. Tetanus is also called lockjaw because it often causes the muscles in the jaw to tighten, which makes it hard for an infected person to open their mouth. Tetanus can also cause fever, difficulty breathing and swallowing, and muscle spasms. Tetanus can be deadly, but vaccination against tetanus is almost 100% effective. 

What is Pertussis?

Pertussis (also called whooping cough) is caused the bacterium Bordetella pertussis. This disease causes a severe and highly contagious cough. Approximately half of infants who get pertussis need to be treated in the hospital. Immunity from the pertussis vaccine decreases over time. With all 5 doses of DTaP, the vaccine is 90% effective at preventing infection. The protection against infection drops to about 70% 5 years later, but it is still very effective for preventing severe disease and hospitalization. 

DTaP vs. Tdap

When D, T, and P are capitalized, it indicates a full strength dose, so DTaP contains full strength doses of all three components, but Tdap only contains a full strength dose of tetanus.


The lowercase "a" stands for acellular, which means the pertussis component does not contain whole cells.  

Tdap Options

What's the difference between them?

5 doses of DTaP are recommended for children at 2 months, 4 months, 6 months, 15-18 months, and 4-6 years

1 dose of Tdap is recommended for children at 11-12 years old, then it is recommended that people get boosters every 10 years. 


Kinrix, Pediarix, Pentacel, Quadracel, and Vaxelis are combination vaccines:

Kinrix and Quadracel also protect against polio

Pediarix also protects against polio and hepatitis B

Pentacel also protects against Hib and polio

Vaxelis protects against polioHib, and hepatitis B 

For more information about DTaP and Tdap vaccination, click here.

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Relevant Terms

  • Acellular: does not use whole cells

  • Bacteria: A type of single-celled organism. Some can cause disease, but many are harmless and some actually benefit humans by living in the intestines and helping with digestion 

  • Bacterium: the singular of bacteria (one bacterium, two bacteria)

  • Muscle Spasms: involuntary muscle tightening or contractions

  • Paralysis: the inability to voluntarily move a muscle

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