The DTaP vaccine is for children (usually infants) under 7 to inoculate them against diphtheria, tetanus and pertussis (whooping cough). Tdap is the booster shot given at age 11 and then throughout life after roughly every 10 years to ensure continued immunity through adolescence and adulthood.
DTaP contains an inactivated form of the toxins produced by the bacteria that causes these diseases. Tdap also contains these inactivated forms, but it contains less of the diphtheria and whooping cough toxins than the DTaP.
edit Vaccination Dosage
Children should receive 5 doses of DTaP: one at 2 months, one at 4 months, one at 6 months, one between 15 and 18 months, and one between 4 and 6 years.
As immunity fades over time, adults are advised to get a booster every 10 years. If they received Tdap as a child, they are advised to get the Td vaccine every 10 years instead.
The CDC suggest that children who are moderately or severely ill at the time they are scheduled for the vaccine should not receive it until they recover. If a child has a life-threatening allergic reaction or suffers a brain disease within seven days of receiving the vaccine, they should not have another dose.
DTaP carries a small risk of allergic reaction. These are seen in less than one out of a million doses, and will happen within a few minutes or hours of taking the vaccine. Symptoms include difficulty breathing, hoarseness, wheezing, hives, planes, weakness, rapid heartbeat and dizziness. Very rare side effects include seizures, coma and brain damage, but these are so rare that the CDC cannot tell whether they are related to the vaccine. Mild side effects include fever, redness, soreness, tiredness and vomiting.
Tdap has similar side effects.