DTaP is a vaccine that helps children younger than age 7 develop immunity to three deadly diseases caused by bacteria: diphtheria, tetanus, and whooping cough (pertussis). Tdap is a booster immunization given at age 11 that offers continued protection from those diseases for adolescents and adults.
Tetanus, or lockjaw, is caused by a bacterium often found in soil. Once it enters the body it releases a toxin that attacks the nervous system, causing muscle spasms and death if left untreated.
Pertussis, also highly contagious, causes coughing spasms so severe that in infants it makes it difficult to eat, drink, or even breathe. It can lead to pneumonia, seizures, brain damage, and death.
Before the vaccines were developed, these diseases were rampant. Vaccines protect the community by preventing the spread of disease from one person to the next, which even offers some protection to the unvaccinated. If people stopped getting vaccinated, the incidence of these three diseases would rapidly rise and thousands would get sick and perhaps even die.
Both vaccines contain inactivated forms of the toxin produced by the bacteria that cause the three diseases. Inactivated means the substance no longer produces disease, but does trigger the body to create antibodies that give it immunity against the toxins. DTaP is approved for children under age 7. Tdap, which has a reduced dose of the diphtheria and pertussis vaccines, is approved for adolescents starting at age 11 and adults ages 19 to 64. It is often called a booster dose because it boosts the immunity that wanes from vaccines given at ages 4 to 6.
Immunity wears off over time. So, the current recommendation is that everyone needs a booster shot for tetanus and diphtheria every 10 years after first being immunized. That booster comes in the form of a vaccine called Td. But since immunity to pertussis also wears off during childhood, a weaker form of the pertussis vaccine has been added to the booster to make the vaccine Tdap. The current recommendation is that one dose of the Tdap vaccine be substituted for one dose of the Td vaccine between the ages of 11 and 64. Pregnant women are also advised to get the Tdap vaccine, preferably between 27 and 36 weeks' gestation.
Children ages 7 through 10 who aren't fully vaccinated against pertussis, including children never vaccinated or with an unknown vaccination status, should get a single dose of the Tdap vaccine. Teens ages 13 through 18 who haven't gotten the Tdap vaccine yet should get a dose, followed by a booster of tetanus and diphtheria (Td) every 10 years.