It should not be confused with the DTP vaccine, which immunizes against the same diseases but is no longer used in the United States. Similarly, the Tdap vaccine covers the same diseases but is only used for older children and adults.

Why DTaP Replaced DTP

The DTP vaccine has been around since 1948 and was one of the first to combine multiple vaccines into a single injection. It combined the pertussis vaccine (created in 1914) with the diphtheria vaccine (1926) and the tetanus vaccine (1938).

The DTP marked a major turning point in the prevention of these illnesses, reducing the annual incidence of whooping cough alone from 200,000 in the 1940s to just over 20,000 today.

How DTaP Differs

To address these shortcomings, scientists developed a safer version in 1996 known as the DTaP vaccine. The “a” in DTaP stands for the acellular pertussis component of the vaccine. An acellular vaccine, by definition, is one in which a component of a contagion is used instead of a whole, inactivated cell.

While many whole-cell vaccines are safe and effective, the use of the entire contagion means that they are among the crudest of all vaccines. In the case of pertussis, the outer shell of the bacteria is comprised of fats and polysaccharides, which are endotoxic, meaning they can cause a generalized, all-body inflammation.

For this reason, children given the DTP vaccine were sometimes known to experience high fever, febrile seizures (fever-related convulsions), and fainting.

The DTaP vaccine, by contrast, only contains the antigenic components of the cells. Antigens are the proteins that the immune system uses to identify and launch an immune attack. By removing the endotoxins and using only antigens, the DTaP vaccine can spur an immune response with far fewer side effects.

Diseases the DTaP Prevents

Diphtheria, tetanus, and pertussis are all diseases caused by bacteria that, if left untreated, can cause serious illness and death. Diphtheria and pertussis are spread from person to person. Tetanus enters the body through cuts or wounds.

Diphtheria

Diphtheria is caused by Corynebacterium diphtheriae bacteria. It is easily spread through coughing, sneezing, or direct contact with a contaminated object, such as a toy.

Two to five days after exposure, the toxins from the bacteria can cause respiratory symptoms (including a thick, gray coating in the nose or throat), weakness, swollen lymph nodes, and fever. If it enters the bloodstream, it can damage the heart, kidneys, and nerves.

Tetanus

Tetanus is caused by Clostridium tetani bacteria, the spores of which are found in soil, dust, and manure. The contagion enters the body through broken skin, often when the skin is punctured by a contaminated object such as a nail.

Tetanus is often called “lockjaw” because it can cause severe tightening of the jaw muscles. This can lead to serious health problems, making it difficult to swallow or breathe.

Pertussis

Pertussis is caused by Bordetella pertussis bacteria, which attaches itself to tiny, hairlike projections (called cilia) that line the upper respiratory tract. The bacteria release toxins that not only damage the cilia but cause the airways to swell.

Like diphtheria, pertussis is spread by coughing, sneezing, or simply being in the same airspace for an extended time.

Symptoms appear within five to 10 days of exposure and may include low-grade fever, apnea (gaps in breathing), vomiting, fatigue, and a characteristic, high-pitched, “whooping” cough. Pneumonia (infection of the lungs) can also develop.

Because their names are so similar, people are uncertain if they need the DTaP or Tdap vaccine. Moreover, there are also the DT and Td vaccines, which are used to prevent only diphtheria and tetanus, respectively.

The primary difference in these vaccines is that they are given to different groups. According to the CDC recommendations:

DTaP is recommended for children under age 7 and contains more antigens to better build an immune defense. It is marketed under the brand names Daptacel and Infarix. DT is recommended for children under age 7 in whom the pertussis vaccine is contraindicated (not recommended, usually because there has been a previous allergic response). It is sold as a generic. Tdap is a booster vaccine given to children over age 7 and adults and requires fewer antigens to boost protection. It is marketed under the brand names Adacel and Boosterix. Td is a booster vaccine for tetanus given to adolescents and adults who may be at lower risk of pertussis. It is marketed under the brand name Tenivac.

Immunization Schedule

The DTaP vaccine is given as an intramuscular injection, delivered in the thigh muscle in infants and young children or the deltoid muscle of the upper arm in adolescents and adults.

The number and schedule of doses differ by a person’s age and circumstance:

Infants and children: For infants, five separate shots are scheduled at 2 months, 4 months, and 6 months of age; between 15 months and 18 months old; and between 4 years old and 6 years old. A booster dose of Tdap should then be given when the child is 11 years old to 12 years old. Adults: For adults who have not been immunized, a single Tdap shot can be used. A booster Tdap or Td shot should then be given every 10 years. Pregnancy: Pregnant women should receive a single dose of Tdap in each pregnancy, preferably at 27–36 weeks gestation.

Side Effects

Side effects from the DTaP vaccine tend to be mild and transient, resolving within a day or so in most people. They commonly include:

Low-grade fever Injection site soreness, redness, swelling, or tenderness Tiredness

Symptoms tend to develop one to three days after a shot and are more common after the fourth or fifth injections. The swelling will usually resolve within one to seven days. Less commonly, vomiting can occur.

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