Whooping Cough in Babies: A Pediatrician's Guide to Symptoms, Danger Signs, and Protection

Whooping cough is a very contagious lung infection caused by bacteria. It is most dangerous for babies under 1 year old. About 1 in 3 babies under 1 who get it need care in the hospital. Many babies do not "whoop" at all. Some just stop breathing. The good news: you can protect your baby, and it often starts with the people who already live in your home.

Here is a fact most parents never hear. When doctors can find out where a baby caught whooping cough, the most common source is an older brother or sister. That is why a back-to-school cough in the house is worth taking seriously when there is a baby at home.

What is whooping cough (pertussis)?

Whooping cough is a very contagious lung infection. Doctors also call it pertussis. It is caused by bacteria called Bordetella pertussis. It spreads through the air when someone coughs or sneezes.

Pertussis (the medical name for whooping cough) sticks to the tiny airways in the lungs and releases toxins. This leads to swelling and long bursts of coughing. In older children and adults it can end in a high-pitched "whoop" as they gasp for air. As you will see below, many babies never make that sound. People are most contagious early on, and can spread the bacteria for at least 2 weeks after the coughing starts.

Why is whooping cough so dangerous for babies?

Babies under 1 year old have the highest risk of severe illness from whooping cough, and most whooping cough deaths happen in this age group. Their airways are small, and their bodies cannot fight the infection as well as an older child's can.

Two facts explain the danger. First, the youngest babies have not had their own shots yet, because the vaccine series does not start until 2 months. Second, a baby may not cough the way an older child does. Instead, a baby may simply stop breathing. The CDC reports that most infant whooping cough deaths happen in babies who are too young to be protected by their own vaccine series. That is exactly why protection has to come from the adults and older kids around them.

What are the symptoms of whooping cough in babies?

Whooping cough often starts like a mild cold, then turns into long coughing fits over the next week or two. In babies, the warning signs can be quiet and easy to miss.

Whooping cough usually comes in stages. It can last for weeks. Because of the long cough, it has earned the nickname "the 100-day cough." One tricky part for parents: a baby with whooping cough often looks well in between coughing fits, which can make the illness seem less serious than it is.

Early symptoms (the first 1 to 2 weeks)

At the start, whooping cough looks a lot like a common cold. Early signs can include:

• A runny or stuffy nose
• A mild, occasional cough
• Low fever (the CDC notes it is usually under 100.4°F, if there is any fever at all)
• Sneezing

One useful clue: with whooping cough, fever is usually mild or absent the whole time. Many parents use fever to judge how sick a child is. With this illness, that gauge can fail you. A baby can be seriously ill from whooping cough without ever running a high fever.

Why some babies do not whoop, and may just stop breathing

Many babies with whooping cough do not make the classic "whoop" sound, and some do not cough much at all. The most dangerous sign in a baby is apnea (pauses in breathing).

Here is the clinical detail that makes this the most important section for parents of a baby. The "whoop" is a forceful gasp for air. A baby under 6 months may simply not have the strength to make it. So instead of coughing fits with a whoop, a baby may have:

• Apnea (pauses in breathing)
• Cyanosis (bluish, gray, or pale skin, especially around the lips)
• A struggle to breathe, or gasping
• Long pauses where the baby seems to stop breathing

For some babies, whooping cough may look like a common cold for the entire illness. This is why a baby who is not coughing much is not automatically reassuring. If your baby has pauses in breathing or turns blue or gray, treat it as an emergency (see the "When to call" section below).

How is whooping cough different from croup or a common cold?

Here is the quick difference. A cold is mostly a runny nose and a mild cough. Croup has a barky cough and noisy breathing when a child breathes in. Whooping cough brings long coughing fits that come in bursts. It can last for weeks.

These illnesses can be hard to tell apart at home, especially in a baby. The table below shows the general patterns. If you have covered croup before, you may find our guides on croup symptoms and croup treatment helpful for comparison.

One honest caution: in a baby under 6 months, none of these rules hold reliably. If your baby is very young and something seems off, it is safer to have a clinician look than to guess by the sound of the cough at 2 a.m.

How is whooping cough in babies treated?

Whooping cough in babies is treated with antibiotics. Starting them early matters. Your baby's doctor picks the antibiotic based on your baby's age. For the youngest infants, the CDC's first choice is a medicine called azithromycin.

A few things every parent should understand about treatment:

• Timing is everything. Antibiotics work best when started early, before the worst coughing fits begin. For a baby under 1, the CDC says treatment should start within 6 weeks of when the cough began.
• Doctors often treat a baby on suspicion. Whooping cough is very risky for babies. So a pediatrician may start antibiotics before test results come back, when the signs point to whooping cough. Babies are a high-risk group. Waiting for the cough to prove itself can waste the window when antibiotics still help.
• Antibiotics do not stop the cough. This surprises many parents. Antibiotics can lower how contagious your baby is and can help if given early, but they do not cure the cough itself. Cough and cold medicines do not help either, and are not safe for babies.
• Some babies need the hospital. About 1 in 3 babies under 1 who get whooping cough need hospital care. It is most common in babies under 6 months. In the hospital, care focuses on keeping the airway clear. Staff watch the baby's breathing and give oxygen if needed. They also prevent dehydration with fluids given through a vein.

The treatment window is narrow, and a baby's cough can be hard to read. That is why early contact with a clinician is worth it. A video visit is a good first step. A clinician can hear the cough, decide whether testing or antibiotics are needed, and tell you what to watch for.

How can I protect my baby from whooping cough?

The strongest protection for a newborn is a Tdap shot during pregnancy. Next comes the baby's own DTaP shots. It also helps to keep the people around the baby up to date on their vaccines.

Prevention has a clear order. The single best step is the Tdap shot during pregnancy. It protects your baby in the risky first months, before their own shots start. After that comes your baby's DTaP series. Then comes making sure siblings, grandparents, and caregivers are protected too. If you are also sorting out other early-infancy shots, our guide to the Hep B birth dose decision covers a common newborn vaccine question.

Vaccines are not perfect, and it is fair to have questions. A baby who is vaccinated can still catch whooping cough. But the illness is usually much milder. Both Tdap vaccines used in pregnancy are approved by the FDA for that use. So far, the national vaccine safety system has not found safety concerns for pregnant women or their babies after a Tdap shot.

The DTaP vaccine schedule for babies

Your baby's own protection comes from the DTaP vaccine. It is a series of shots that starts at 2 months old. According to the CDC's pertussis vaccination recommendations, the DTaP schedule is five doses:

• 2 months
• 4 months
• 6 months
• 15 to 18 months
• 4 to 6 years

The CDC's immunization schedule notes the earliest a first dose can be given is 6 weeks, if your baby's doctor recommends it. But the routine start is 2 months, and how early to begin is a decision for your pediatrician. Older kids get a Tdap booster at 11 to 12 years, which helps keep them from bringing whooping cough home to a younger sibling.

Tdap during pregnancy and "cocooning" the people around your baby

The most important protection for a newborn happens before birth. The CDC recommends a Tdap shot during every pregnancy, ideally early in weeks 27 to 36. The shot helps the pregnant parent make protective antibodies. These antibodies cross to the baby before birth. They cover the gap in the first months of life, before the baby's own shots begin at 2 months.

A few points parents often ask about:

• Getting a Tdap shot in the third trimester prevents more than 3 in 4 cases of whooping cough in babies under 2 months. It prevents about 9 in 10 of the cases that would have put a baby in the hospital.
• A Tdap shot after delivery does not pass protection to your baby the way a shot during pregnancy does. It is still worth getting if you missed the window during pregnancy. It protects you from catching whooping cough and passing it to your baby, which is part of cocooning. It takes about 2 weeks to work.
• One shot per pregnancy, every pregnancy, even for back-to-back pregnancies.

The second layer of protection is called "cocooning." That means making sure everyone close to your baby is up to date on their whooping cough vaccine. This includes parents, siblings, grandparents, and caregivers. It takes about 2 weeks to build protection after a shot. So anyone who needs one should get it at least 2 weeks before meeting the baby.

Cocooning matters, but the CDC is clear that cocooning alone may not be enough. That is why the Tdap shot during pregnancy comes first. This is also where the back-to-school angle becomes real. When researchers can find where a baby caught whooping cough, most sources are family members. The most common single source is an older sibling. The person most likely to bring this infection home may already live in your house.

When should I call the doctor or go to the ER?

Some whooping cough signs in a baby are a true emergency, and some mean you should call your pediatrician the same day. Knowing the difference helps you act fast without panicking.

A baby who is turning blue, gasping, or pausing their breathing needs emergency care right away. This is not something a video visit can handle. Call 911 or go to the nearest ER if your baby has any of these signs:

• Your baby stops breathing, or pauses between breaths (apnea)
• Your baby's lips, face, or nail beds look blue, gray, or pale
• Your baby is struggling to breathe, or is gasping
• Your baby is limp, unresponsive, or very hard to wake

Call your pediatrician today (a telehealth visit is a good first step) if your baby has any of these signs:

• A cough that comes in fits, or that is getting worse and more frequent
• Your baby vomits after coughing
• Your baby is worn out after coughing, feeding poorly, or looks sick
• Your baby has been around someone with whooping cough or a long-lasting cough
• Your baby is not fully vaccinated
• Someone in your home has been diagnosed with whooping cough, even if your baby seems well

A video visit is a good first step when your baby is breathing comfortably between coughs. A clinician can hear the cough, decide whether testing or antibiotics make sense, and tell you what to watch for. A video visit is not the right choice for a breathing emergency. It also cannot confirm whooping cough on its own, because that needs a swab or blood test. Blueberry pediatricians can help with early triage of a worrying cough, so you know what to do next.

Frequently asked questions

Is whooping cough contagious, and for how long?

Yes, and very much so. The CDC says people can spread the bacteria from the start of symptoms and for at least 2 weeks after the coughing begins. Starting antibiotics early can shorten how long someone is contagious. The AAP advises keeping a child home from school or child care until they have finished 5 days of antibiotics.

What does whooping cough sound like in a baby?

In older children it can end in a high-pitched "whoop" as they gasp for air. Many babies never make that sound. The CDC notes that babies younger than 6 months may not have the strength to whoop, and many babies do not cough much at all. Instead they may pause their breathing or turn blue.

At what ages does a baby get the DTaP vaccine?

The CDC's schedule is five doses: 2 months, 4 months, 6 months, 15 to 18 months, and 4 to 6 years. The first dose can be given as early as 6 weeks if your baby's doctor recommends it.

How does a Tdap shot during pregnancy protect a newborn?

Antibodies cross to the baby before birth. They cover the gap before the baby's own shots start at 2 months. The CDC recommends Tdap in every pregnancy, ideally early in weeks 27 to 36. A CDC evaluation found it prevents more than 3 in 4 cases of whooping cough in babies under 2 months when the shot is given in the third trimester. It prevents about 9 in 10 of the cases that would have put a baby in the hospital.

What is "cocooning"?

Cocooning means making sure everyone close to your baby is up to date on their whooping cough vaccine. That includes parents, siblings, grandparents, and caregivers. The CDC recommends getting vaccinated at least 2 weeks before meeting the baby. The CDC is also clear that cocooning alone may not be enough. That is why the shot during pregnancy matters most.

Can my baby still get whooping cough if they are vaccinated?

Yes, but it is usually milder. The CDC says the vaccines work well, but protection fades over time. People who are vaccinated and still get whooping cough generally have a milder illness.

My baby is not 2 months old yet. What protects them right now?

Two things protect them right now. The first is the Tdap shot you got during pregnancy. The second is making sure everyone around your baby is up to date on their own whooping cough vaccine. CDC research found that when a source can be found, most babies catch it from a family member. Most often, that is an older sibling.

My older child was just diagnosed with whooping cough. What about the baby?

Call your baby's pediatrician the same day, even if your baby seems well. When someone in your home has whooping cough, your baby and other family members may need preventive antibiotics to keep from getting sick, even if they are vaccinated. Do not wait for your baby to start coughing. Starting antibiotics early can protect a newborn who was exposed.

A note from Blueberry Pediatrics

Whooping cough is one of the illnesses where a baby's cough can be hard to read, even for a doctor. It often does not look dramatic at first, and a baby can seem well between coughing fits. That is the exact reason our pediatricians do not wait for a cough to "prove" itself in a young baby. When a parent describes coughing fits, feeding trouble, or any pause in breathing, we would rather see the baby early and decide together what to watch for.

Sources

• CDC. Symptoms of Whooping Cough. Updated December 2, 2025.
• CDC. Clinical Features of Pertussis. Updated December 1, 2025.
• CDC. Treatment of Whooping Cough (consumer). Updated December 2, 2025.
• CDC. Clinical Care of Pertussis. Updated December 2, 2025.
• CDC. Pertussis Vaccination Recommendations. Updated December 2, 2025.
• CDC. Vaccinating Pregnant Patients. Updated December 2, 2025.
• CDC. Types of Whooping Cough Vaccines. Updated December 2, 2025.
• CDC. About Whooping Cough.
• CDC. Child and Adolescent Immunization Schedule by Age.
• American Academy of Pediatrics, HealthyChildren.org. Whooping Cough (Pertussis): Symptoms, Treatment and Prevention. Last updated March 4, 2026.
• Skoff TH, Kenyon C, Cocoros N, et al. Sources of Infant Pertussis Infection in the United States. Pediatrics. 2015;136(4):635 to 641. PMID 26347437. (Siblings, parents, and caregivers as common infant sources of infant pertussis.)