Tdap Vaccine During Pregnancy: When It Is Used, How It Works, Is It Safe? - Verywell Health

The Tdap vaccine is a combination vaccine against tetanus, diphtheria, and pertussis (commonly known as whooping cough). The Centers for Disease Control and Prevention (CDC) recommends that pregnant people receive the Tdap vaccine during the final trimester of pregnancy.

When the Tdap vaccine is given between 27 and 36 weeks of pregnancy, antibodies against whooping cough are passed to the fetus. Studies have found that prenatal Tdap vaccination significantly lowers a newborn's risk of contracting whooping cough in the first two months of life.

The Tdap vaccine is safe for pregnant people. Research has shown that the vaccine does not adversely affect pregnancy, birth, or neonatal outcomes. Additionally, being pregnant does not increase the risk of having a reaction to the vaccine.

Here's what you should know about getting the Tdap vaccine while you are pregnant.

Marina Demidiuk / Getty Images.

What Is in the Tdap Vaccine?

The U.S. Food and Drug Administration (FDA) licensed the Tdap vaccine for use in adolescents and adults in 2005. It protects against three diseases: tetanus, diphtheria, and pertussis (whooping cough). 

The FDA licenses several tetanus vaccine combinations. Here are the combinations and who is approved to receive them:

• Tdap: Pregnant people, adults, and kids over age 7 
• DTaP: Children ages 6 weeks through 6 years
• DT: Children who can not receive the pertussis vaccine
• Td: As a booster shot for adults and children over age 7

What do the letters mean?

The upper case letters in the vaccine combination indicate the full-strength component of the vaccine. The lower-case "a" in the Tdap and DTaP vaccines stands for "acellular," which means that the pertussis component contains only part of the bacteria rather than the whole.

Tetanus

Tetanus is an illness that is caused by bacteria. The bacteria produce toxins in the body that cause muscle contractions which can make the muscles in the head and neck seize up. The contractions can make it difficult to open your mouth or swallow, which is why tetanus is also called "lockjaw."

You cannot catch tetanus from someone who has it (it is not contagious). A person gets tetanus when the bacteria is picked up in soil, dust, or manure and enters their skin through an opening (often a puncture wound).

Tetanus is rare—only about 30 cases are reported in the United States every year. Nearly all cases occur in unvaccinated people, including adults who have not kept up with their 10-year tetanus booster shots.

There are serious complications of tetanus, including fractures, pulmonary embolism, aspiration pneumonia, and difficulty breathing. Up to 20% of cases are fatal.

Diphtheria

Diphtheria is also caused by bacteria that create a toxin in the body. The bacteria infect the respiratory tract and skin and cause a thick coating in the throat that makes it hard to breathe. 

Diphtheria is contagious and spreads through respiratory droplets. You can also get diphtheria if you touch the open sores of someone who is infected.

Thanks to vaccines, diphtheria is almost unheard of in the United States. However, it is still a public health concern in other parts of the world. In 2018, there were 16,000 reported cases of diphtheria globally.

Diphtheria infection can lead to airway obstruction; nerve, heart, and kidney damage; and paralysis. About 10% of cases are fatal. For untreated diphtheria, the fatality rate can be as high as 50%.

Pertussis

Pertussis, commonly known as whooping cough, is a bacterial respiratory infection. The disease causes violent, uncontrollable coughing that causes people to make a classic "whoop" sound when they gasp for breath. 

Whooping cough is communicable. It is highly contagious and is spread through contact with an infected person when they cough or sneeze.

Pertussis is common. The most recent large outbreak in the United States was in 2012 when more than 48,000 cases were reported.

The disease is usually mild in adults, but it can be deadly for babies under 1 year old, especially if they have not received their pertussis vaccine. 

Pertussis can lead to pneumonia, convulsions, apnea, and brain swelling. About half of infants with whooping cough will require hospital treatment and about 1% of them will die.

When It's Used

The combination vaccine is recommended for everyone, beginning in infancy. Children who follow the vaccine schedule will receive five shots from 2 months of age through the age of 4 to 6.

Adults require a booster shot every 10 years. However, pregnant people should get a Tdap vaccine in the last trimester of every pregnancy. This ensures that the fetus receives the immune benefits the vaccine offers from birth until they receive their first pertussis vaccine when they are 2 months old.

How It Works

When the Tdap vaccine is given between 27 and 36 weeks gestation, it produces an antibody response in a pregnant person's body that provides passive antibody transfer to the fetus.

In 2013, the Advisory Committee on Immunization Practices (ACIP) of the CDC began recommending that pregnant people receive the Tdap vaccine during each pregnancy.

Using the Tdap vaccine in pregnancy to provide passive immunity to a newborn is very effective. A 2016 study found that pertussis-infected infants of vaccinated parents were less likely to require hospitalization. Those that did require hospitalization had shorter hospital stays, and none of the infants required intubation or died.

Another study in 2017 found that Tdap vaccination in pregnancy reduced the risk of pertussis infection in a newborn by 91%. It also showed that maternal Tdap vaccination continued to offer benefits throughout the first year of life by reducing pertussis risk by 69%.

The researchers noted that the effectiveness of Tdap vaccination during pregnancy in preventing pertussis in the first 2 months of life was 88%.

Is It Safe?

Research has determined that Tdap vaccination in pregnancy is safe. There is no evidence that the vaccine causes adverse effects on the fetus.

There is no evidence that the Tdap vaccine increases the risk of autism and it does not contain the mercury component, thimerosal.

A retrospective observational cohort study from 2010 to 2012 did find a slightly increased risk of an intrauterine infection called chorioamnionitis among people who had been vaccinated with Tdap, but there was no increase in the preterm birth rate among those people.

It's also important to note that other analyses did not find any difference in chorioamnionitis between vaccinated and unvaccinated groups. 

In addition, the pregnancy reports of chorioamnionitis in the Vaccine Adverse Event Reporting System (VAERS) database between 1990 and 2014 found that 58% had preexisting risk factors. The Tdap vaccine did not increase other adverse pregnancy outcomes. No significant birth and neonatal outcomes were associated with Tdap vaccination during pregnancy.

Common Side Effects

A review of prospective clinical trials and database analyses has identified commonly reported injection site reactions among people who receive the Tdap vaccine. However, it is not believed that pregnancy increases the rate of these reactions.

Possible injection site reactions after the Tdap vaccine include:

• Pain
• Swelling
• Itching
• Redness

There is conflicting evidence about fever following Tdap vaccination during pregnancy. One study found that up to 5% of pregnant people reported that they had a fever after receiving the pertussis vaccination. The results also suggested that pregnant people who received the Tdap shot might be five times more likely to visit a healthcare provider for a fever.

However, another study did not find any difference in fever between prenatal Tdap and placebo groups.

Research has also shown that when someone receives Tdap in shorter intervals—such as when pregnancies occur closer together—side effects do not increase. The exception is muscle pain, which was increasingly reported by people in this group.

A Word From Verywell

Receiving a Tdap vaccination between 27 and 36 weeks gestation is a safe and effective way to protect a newborn against pertussis from birth until they receive their first vaccine at 2 months of age.

The World Health Organization (WHO), the CDC, and the American College of Obstetricians and Gynecologists (ACOG) all recommend routine vaccination during each pregnancy to prevent whooping cough in very young babies.

The most significant risk of whooping cough is to babies under 1 year. You can be proactive about protecting your baby by getting your Tdap shot during pregnancy and follow the childhood vaccine schedule once your baby is born.

If you have concerns or questions about vaccination during pregnancy, talk to your doctor. They will be able to address your concerns and can give you the Tdap vaccine at a prenatal appointment. 

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