What it prevents: This vaccine prevents against three deadly diseases.

Diphtheria: Caused by a bacterium that usually collects in the throat, the early symptoms are a sore throat, fever, and swollen neck. As the infection progresses, a gray membrane forms (usually in the throat, but it can also occur elsewhere in the body) which can block the airway, making it impossible for the person to breathe. The infection can then spread through the blood causing pneumonia, muscle paralysis, and heart and kidney failure.

Tetanus: Also known as lockjaw, tetanus causes severe continuous muscle spasms throughout the body. An infection results when the bacteria (found in both human and animal feces as well as soil) enters the body through a deep skin wound. It can lead to complications with breathing as well as pneumonia and in rare cases, even death.  

Pertussis: Also known as whooping cough, pertussis causes severe coughing and may progress to pneumonia and even death.

When it’s given: There are five DTaP shots: The first three are given at ages two months, four months, and six months of age; the fourth is given between 12 and 18 months, and the last is given between four and six years. The first three shots of DTaP can also be given as part of a combination shot with the Hep B and IPV vaccines. A booster shot of Td (tetanus-diphtheria) is needed every 10 years, however, older children (between the ages of 11 and 18) who have received the entire DTaP series should receive a booster that also contains pertussis, known as Tdap.) Parents and caregivers should also receive a Tdap shot to protect newborns from exposure to pertussis (whooping cough) before they are fully immune.

What you may have heard: An older form of the shot – the DTP shot, was more likely to cause side effects, such as a fever, because it contained whole cells of the pertussis bacterium. However, the current shot, DTaP, licensed for use by the FDA in 1991, contains only small components of the cell (it’s called “acellular” Pertussis), so it’s much less likely to cause a reaction. 

In the United States, there has been an uptick in cases of pertussis in recent years, because the immunity that the vaccine provides starts to wear off after about ten years. While a teen or an adult can usually fend off a case of pertussis, it can be deadly in a baby. And babies aren’t fully protected against pertussis until they’ve had their third shot at six months. For this reason, the CDC recommends that teens and adults, especially parents and caregivers of babies, receive a booster of the vaccine to protect infants by creating a “cocoon” of immunity.

You also may have heard about outbreaks of diphtheria that have occurred in Russia and Eastern Europe in areas where vaccination levels have fallen. This is a scary reminder of how quickly these diseases can pop up again when vaccine rates start to fall in a community.

Risk of a reaction: About 50 percent of children receiving the DTaP vaccine will not experience a reaction to the vaccine; the other 50 percent may experience a mild reaction, such as soreness at the injection site, fever, or upset stomach. The last two doses of the DTaP vaccine have on rare occasions been linked to a temporary swelling of the limb where the shot was given.  About 1 percent of children receiving the shot may have a more severe reaction, such as a seizure or a high fever.