Tdap vs. DTaP: What’s the Difference Between These Whooping Cough Vaccines?

Updated: Aug. 21, 2023

DTaP and Tdap vaccinate against the same illnesses: diphtheria, tetanus, and pertussis (aka whooping cough). So why are there two?

Tdap vs. DTaP

Over the past century, vaccines have eradicated some truly horrific diseases like smallpox from the face of the earth. Today, the small vials of serum still prevent as many as five million deaths annually around the globe, according to the World Health Organization.

One important vaccine for children and adults combines diphtheria, tetanus, and pertussis (aka whooping cough).

The vaccine comes in two versions: DTaP, which stands for Diphtheria, Tetanus, and acellular Pertussis; and Tdap, which stands for Tetanus, diphtheria, and acellular pertussis. As you can probably guess, it’s pretty easy to mix up the two shots. (“In some rare cases, people may have an allergy to the pertussis component of the DTaP,” notes Linda Yancey, MD, an infectious diseases specialist at Memorial Hermann Hospital. “In this case they can be given the Td vaccine—but it is much better to get that pertussis protection that comes with the DTaP so only ask for a Td if you know you’re allergic to pertussis.”)

Here’s what you need to know about the differences.

Both vaccines prevent the same diseases

Confusion over the vaccines stems from their use: Both prevent the same three bacteria-caused diseases.

Whooping cough symptoms are right there in the name. Infection by pertussis leads to fits of coughing so severe they can crack ribs in adults and land small children in the hospital. The “acellular” part of DTaP and Tdap acronyms indicates that only pieces of the pertussis bacterium are used in the vaccine—not the whole bug.

“This is a very scary disease in the very young,” says Dennis Cunningham, MD, system medical director of infection control and prevention at Henry Ford Health System in Detroit.

The bacterium that causes tetanus, or “lockjaw,” gets in through your skin and can trigger spasms in muscles throughout your body.

You can pick up tetanus from things like rusty nails, says Dr. Cunningham. Step on one, and you could get tetanus.

Diphtheria is rare in the United States today, but it results in a high fever and blocked airways that Dr. Cunningham says can be “life-threatening and hard to treat.”

(Read the 40 things doctors wish you knew about vaccines.)

The vaccines have saved millions of lives

Because the vaccines are so effective, people sometimes think of the trio as old diseases they’re surprised still exist.

Before a vaccine came out in the 1920s, the United States had more than 200,000 cases of diphtheria and more than 15,000 deaths each year.

Today? The Centers for Disease Control and Prevention (CDC) reports that there have only been three U.S. cases in the last decade.

We’ve seen similar successes for the tetanus vaccine. Cases are down from about 500 to 600 cases a year to about 30 now, almost all in unvaccinated people.

Whooping cough had a similar decline, from about 200,000 cases before the vaccine was licensed in the 1940s to an all-time low of just over 1,000 cases in 1976. Unfortunately, cases have curved up again as more people skip vaccinations. In 2012, the CDC reported almost 50,000 cases of pertussis in children and 13 deaths.

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The vaccines are for different age groups

The most important difference between the vaccines is who gets them. “Medically speaking, we call the adult version Tdap and the children’s version DTaP,” says Richelle Schiro, MD, a family medicine physician and chair of the Vaccine Committee at Ochsner Health in Abita Springs, Louisiana.

Specifically, DTaP is for children younger than seven, while Tdap is for everyone older than that, including adults and pregnant women.

The initial childhood series of DTaP starts at two months of age. Four more doses are given at the ages of four months, six months, 15 to 18 months, and four to six years.

Kids should also get a booster of Tdap when they’re 11 or 12 years old and every 10 years thereafter.

Parents need to be up to date on immunizations too. Adults should get a Tdap booster every decade. (It’s not too late to get your first shot when you’re older.) “The general guideline is to get a booster every ten years because you don’t know if your immunity is waning without a blood test,” explains Dr. Yancey. “There are titers that can be run to test for immunity but they are harder to find and more expensive than the shot itself.  It is far easier just to get the shot. If you’re not sure when your last shot was, err on the safe side and get one. There is no harm in getting vaccines less than 10 years apart. You could safely get one a year, every year.”

Pregnant women need a shot every time they are pregnant to protect the baby.

(Here’s what you need to know about the Tdap vaccine in pregnancy.)

The vaccines are made differently

The reason for these age recommendations is that the components of each vaccine come in different strengths, Dr. Schiro says.

The differences are reflected in which letters are capitalized. The upper-case letters of DTaP means children get full-strength doses of each component.

“The DTaP vaccine has more proteins in it and makes a more robust immune response,” Dr. Cunningham says. Children’s immune systems are still developing and need the extra push.

Lowercase letters mean smaller doses for adults who have fully developed immune systems. In adults, the full dose would give too much of a reaction, Dr. Cunningham says.

(A third vaccine—Td for adults and TD for children—is also an option, though it doesn’t protect against whooping cough.)

Both vaccines are highly effective

According to the CDC, 80 to 90 percent of babies and infants are fully protected after getting the five doses of the original DTaP series.

Five years out, though, only about seven in 10 kids have that full protection, which is why boosters are recommended.

An estimated 70 percent of people who get the Tdap vaccine are protected in the first year after getting the shot. Like DTaP, though, this decreases over time.

(Before you travel, learn about these nine immunizations.)

The side effects are similar

Most of the side effects of the DTaP and Tdap vaccines are mild, including a sore arm and low fever. Small children may be cranky and tired afterward, or they may not want to eat.

In very rare cases, a child may develop a higher fever, constant crying, seizures. Also rare: something called “floppy baby,” where the baby just lies listlessly for a while. This was much more common with an older version of the whooping cough component of the vaccine.

Tell your provider if you or your child have had allergic reactions to the vaccine or any component, or if you have a neurological problem like Guillain-Barré syndrome, in which the immune system mistakenly attacks nerves, leading to weakness, tingling, pain, and even paralysis.

Reschedule the vaccine if you’re currently sick with something more severe than a cold.

The vaccines are safe

Any side effects from DTaP and Tdap are temporary. There are no long-term safety issues, Dr. Cunningham says.

There’s also absolutely no link with autism, he stresses. The advocacy organization Autism Speaks agrees, stating that vaccines have no effect on the development of autism.

“Scientists have conducted extensive research over the last two decades to determine whether there is any link between childhood vaccinations and autism,” the organization says. “The result of this research is clear: vaccines do not cause autism.”

Where to get the vaccines

Children typically get the vaccines at their pediatrician’s office, along with other childhood vaccines. They’re usually also available at family practice offices, community health centers, and public health offices.

Adults can also get the vaccine from their doctors, but pharmacies are another good source, along with community health clinics and health departments.

Make sure your name gets on any state or local registries so you can keep track of what vaccines you’ve had and when you received them. Your doctor should also have a record.

Next, learn about nine vaccinations you need and aren’t getting.