Is Whooping Cough Deadly? Who’s Most at Risk

Whooping cough can be deadly, and the overwhelming majority of deaths occur in infants younger than four months old, who account for roughly 86% of all pertussis fatalities.¹ For older children and healthy adults, the disease is rarely fatal but can cause weeks or months of misery. The gap between those two realities, a nuisance illness for some and a life-threatening emergency for others, is what makes whooping cough such a persistent public health problem even in countries with high vaccination rates.

Why Very Young Infants Face the Greatest Danger

Newborns arrive with almost no immune defense against Bordetella pertussis, the bacterium that causes whooping cough. The routine childhood vaccine series doesn’t start until two months of age, and protective immunity doesn’t build meaningfully until the second or third dose. That leaves a window of several months during which an infant’s airways are tiny, their cough reflex is weak, and their immune system is essentially unarmed.

In young infants, whooping cough can trigger apnea (pauses in breathing), seizures, brain swelling, pneumonia, and death.¹ A study of hospitalized children with severe pertussis found that the median age of patients was just two months, with over 90% under six months old. Among the 38 children admitted to intensive care, 13 died, and more than three-quarters of those deaths were in babies younger than six weeks.² A Spanish national study spanning two decades found that every single death from whooping cough occurred in infants under four months old.³

One of the mechanisms behind these deaths is a surge in white blood cells called leukocytosis. In severe infant pertussis, white blood cell counts can climb to extreme levels, thickening the blood and contributing to pulmonary hypertension and cardiovascular collapse. Exchange transfusion, a procedure that replaces a portion of the infant’s blood, has shown some promise when started early in the course of cardiopulmonary failure, but infants who received the procedure late did not survive.⁴ Even with exchange transfusion, white blood cell counts sometimes rebounded sharply within a day or two in infants who ultimately died.⁵

What the Disease Actually Looks Like

Whooping cough begins deceptively. The first week or two resembles a mild cold: runny nose, low-grade fever, an occasional cough. Then the cough transforms. It becomes paroxysmal, meaning it arrives in rapid, violent bursts during which the person cannot draw a breath. At the end of a coughing fit, the desperate inhale through a swollen airway produces the distinctive “whoop.” Vomiting after a fit is common, and several paroxysms can stack up within minutes, leaving the patient exhausted. This stage can last for weeks, sometimes stretching beyond two months before gradually tapering off.⁶

The coughing fits are not just uncomfortable. In infants, repeated oxygen deprivation during paroxysms can cause encephalopathy, which the CDC has reported in about 0.4% of hospitalized infant cases. Of those infants who develop pertussis encephalopathy, roughly a third die during the acute illness, and another third survive with permanent brain damage. Hospitalization for pertussis has also been linked to an approximately doubled risk of epilepsy by age ten.⁶

Adults and Older People Are Not Immune to Serious Illness

The conversation about whooping cough deaths centers on babies for good reason, but adults get sick too, and some get very sick. Pertussis is increasingly recognized as a significant respiratory infection in older adults, with some experiencing serious complications and even death.⁷ Immunity from childhood vaccination fades over time, and the boosters most adults received in adolescence do not last forever either. That means a grandparent or middle-aged adult can contract pertussis, often without recognizing it as anything more than a stubborn cough.

A large French study of whooping cough hospitalizations between 2008 and 2020 found that among hospitalized adults, more than 62% had asthma or chronic obstructive pulmonary disease (COPD), about 16% had an immunocompromising condition, and about 12% had diabetes. For adults with asthma or COPD, the hospitalization rate for whooping cough was roughly 18 times higher than for adults without those conditions.⁸ Among children and adolescents in the same study, the highest hospitalization rates were in those with immunocompromising conditions, at about 3.6 times the baseline rate.

The picture that emerges is that while death from whooping cough in healthy adults is rare, the disease is far from trivial. Broken ribs from coughing, urinary incontinence, hernias, and weeks of lost work are common adult consequences. For anyone with lungs already compromised by chronic disease or an immune system suppressed by medication or illness, the stakes climb steeply.

Why Whooping Cough in Adults Often Goes Unrecognized

One of the reasons pertussis keeps circulating is that adults frequently carry and spread it without ever being diagnosed. In older children and adults, the classic “whoop” is often absent; the illness just presents as a persistent cough that won’t go away. A study examining the diagnostic value of symptoms and lab results in adolescent and adult patients found that clinical symptoms alone were of limited value in distinguishing pertussis from other causes of cough, making it clinically difficult to differentiate patients with or without the disease.⁹

This matters because an adult with an undiagnosed case can easily transmit the bacterium to an unvaccinated or incompletely vaccinated infant at home. Despite the fact that reinfection in adults (even those previously vaccinated or previously infected) is not uncommon, clinical suspicion of pertussis in adults remains low.¹⁰ Identifying the disease early in an adult not only helps that person get appropriate treatment but also breaks the chain of transmission to vulnerable infants.

What Antibiotics Can and Cannot Do

You might expect that since whooping cough is caused by a bacterium, antibiotics should solve the problem. The truth is more frustrating. Antibiotics are effective at clearing Bordetella pertussis from the throat and nose, which means a treated person stops being contagious sooner. But they do not change the clinical course of the illness itself once the coughing paroxysms have set in. Shorter courses of antibiotics (three to five days of azithromycin, or seven days of clarithromycin or erythromycin) work about as well as the traditional 10-to-14-day course for bacterial clearance, with fewer side effects.⁶ The main value of antibiotics, then, is in limiting spread rather than in relieving symptoms. This is why prevention through vaccination is so much more important than treatment.

Vaccination During Pregnancy Protects Newborns

Because the most dangerous period for whooping cough is before an infant can be fully vaccinated, the most effective strategy for protecting newborns is vaccinating the pregnant parent. When a pregnant person receives a Tdap booster (the combination vaccine for tetanus, diphtheria, and pertussis), they produce antibodies that cross the placenta and provide the infant with temporary protection during those critical first weeks and months.

A study measuring antibody levels in infants born to vaccinated versus unvaccinated mothers found that at two months of age, key pertussis antibody concentrations were dramatically higher in the vaccinated group. For example, antibodies against pertussis toxin were over twelve times higher in the infants of vaccinated mothers compared to those of unvaccinated mothers.¹¹ In terms of actual disease prevention, a study of prenatal Tdap vaccination found an effectiveness of about 93% against pertussis in infants whose parents were vaccinated between 27 and 36 weeks of pregnancy.¹²

There is a tradeoff worth knowing about. The high levels of maternal antibodies circulating in the infant at the time of their own early vaccine doses can slightly dampen the infant’s own immune response to some pertussis antigens after their primary vaccine series. One study found that after the third infant dose, antibody levels against pertussis toxin were actually somewhat lower in the maternal-Tdap group compared to the unvaccinated group.¹¹ This “blunting” effect has been a subject of ongoing research, but the medical consensus is clear: the immediate protection provided to the most vulnerable newborns outweighs the modest reduction in some antibody titers after the primary series.

Cocooning Versus Prenatal Vaccination

Before prenatal vaccination became standard, the main strategy for protecting newborns was “cocooning”: vaccinating everyone in close contact with the baby, including parents, grandparents, and siblings. The logic was to eliminate potential sources of infection in the infant’s immediate environment. Modeling research on asymptomatic transmission, however, has suggested that cocooning may be less effective than hoped, partly because vaccinated people can still carry and transmit the bacterium without showing symptoms.¹³

Cost-effectiveness analyses have compared the two approaches. A Spanish study found that vaccinating pregnant women directly was substantially more efficient than the cocooning strategy. To prevent one infant hospitalization through cocooning, nearly 4,800 parents would need to be vaccinated, versus about 1,300 pregnant women under the prenatal strategy. To prevent one death, the numbers were over 900,000 parents for cocooning compared to 200,000 pregnant women for prenatal vaccination.¹⁴ Both approaches reduce disease burden, but prenatal vaccination delivers more protection per dose.¹⁵

Waning Immunity and Evolving Bacteria

Even in countries with high vaccination coverage, whooping cough has not gone away. Periodic outbreaks continue to flare, and two factors are widely discussed as explanations. The first is waning immunity. Protection from acellular pertussis vaccines, the type used in most high-income countries since the 1990s, fades more quickly than protection from the older whole-cell vaccines. The increase in pertussis cases is most visible in age groups where immunity has had time to wane, particularly adolescents and young adults.¹⁶

The second factor is the bacterium itself. In the United States, most circulating strains of B. pertussis have lost expression of pertactin, one of the key antigens targeted by acellular vaccines. These pertactin-deficient strains have acquired multiple independent mutations disrupting the pertactin gene, which is strong evidence of evolutionary pressure from the vaccine. In laboratory and animal models, pertactin-negative strains show a fitness advantage over pertactin-positive strains in hosts vaccinated with acellular vaccines.¹⁷ ¹⁸ This does not mean current vaccines are useless; they still reduce severity and prevent most deaths. But the shift highlights why whooping cough remains a moving target.

Low-Birthweight Babies and Socioeconomic Factors

Beyond age and vaccination status, other risk markers shape who gets the worst of whooping cough. A case-control study found that low birthweight (under 2,500 grams) was significantly more common among pertussis cases than among controls, as was high birth order (fourth child or later). Male sex and low socioeconomic status were also more frequent among cases.¹⁹ These findings likely reflect a combination of biological vulnerability (premature or low-birthweight infants have less robust immune function) and systemic barriers to timely vaccination and healthcare access.

Global data reinforces the disparity. A systematic analysis using Global Burden of Disease data found that in 2019, the adult pertussis incidence rate in low-income countries was roughly four and a half times the rate in high-income countries.²⁰ The gap narrowed by 2021, but relative disparities persisted, reflecting differences in vaccine access, healthcare infrastructure, and surveillance. In many low-resource settings, cases and deaths from pertussis are likely underreported, so the true burden may be even larger than the numbers suggest.

How Much Has Vaccination Changed the Picture Historically

Before pertussis vaccines became widespread in the 1940s, whooping cough was among the leading killers of children. In the United States, the infant mortality rate from pertussis was about 4.5 deaths per 1,000 live births in 1900. Death rates had already been declining before the vaccine arrived, dropping about 70% between 1900 and the late 1930s, likely due to improvements in nutrition, sanitation, and supportive care.²¹ But the vaccine dramatically accelerated that decline. Based on the pre-vaccine trend, researchers estimated that 4,000 to 8,000 pertussis deaths should have occurred in the United States during the early 1970s; instead, only 52 were recorded.²¹ Historical data from the early twentieth century also show that while mortality was always highest in infants, rates in children aged one to four were about one-tenth as high and declined even more steeply over the same period.²²

Bordetella parapertussis and Why It Adds Confusion

Not every case of “whooping cough” is caused by the same bacterium. Bordetella parapertussis is a related species that can produce a clinically similar illness, complete with the characteristic whoop and paroxysmal cough. An older study comparing the two in an immunized population found no statistically significant differences in the frequency of whooping, vomiting, or the duration of coughing episodes between B. pertussis and B. parapertussis infections at the time of sampling.²³ Historically, parapertussis has been considered the milder cousin, diagnosed less frequently and with a shorter overall course.²⁴

However, a more recent and larger retrospective study complicates that picture. After matching for age and other factors, the B. parapertussis group overall had higher odds of hospitalization and critical care admission compared to the B. pertussis group. The relationship differed by age: in infants under one year, B. pertussis was associated with more hospitalizations, but in children aged one to four and five to seventeen, B. parapertussis was associated with substantially higher odds of hospitalization.²⁵ Pertussis vaccines do not provide meaningful cross-protection against parapertussis, so even fully vaccinated children can be susceptible. This is one reason a child can get “whooping cough” despite being up to date on vaccines.

Long-Term Effects and What Recovery Looks Like

Parents understandably worry about lasting damage after an infant survives a severe bout of whooping cough. The neurological complications described earlier, encephalopathy and seizures, can leave permanent effects when they occur. But for the majority of children who recover from pertussis without those severe neurological events, the long-term respiratory outlook appears reassuring. A British study tracking a nationally representative sample found no long-term detrimental effect of whooping cough on the respiratory system.²⁶ That said, the cough itself can linger for months, and some adults report rib fractures, hernias, or pelvic floor dysfunction from prolonged coughing episodes. Full recovery is the norm for most cases, but it can be a long and unpleasant road.

Next-Generation Vaccines on the Horizon

Given the limitations of current acellular vaccines, especially their waning immunity and the bacterium’s ability to evolve around them, researchers are developing new approaches. One of the most promising is BPZE1, a live attenuated vaccine delivered as a nasal spray. In a phase 2b human challenge trial, a single nasal dose of BPZE1 prevented infection by virulent B. pertussis and substantially reduced bacterial load in the respiratory tract. The vaccine produced both systemic and mucosal immune responses, which current injected vaccines do not reliably achieve.²⁷ In animal studies, a similar genetically altered vaccine prevented not just disease but colonization of the airways, which could mean vaccinated individuals would be far less likely to silently carry and spread the bacterium.²⁸ If these vaccines reach the market, they could address the two biggest gaps in current pertussis control: the fading protection that leaves adolescents and adults vulnerable, and the asymptomatic transmission that keeps the bacterium circulating even in highly vaccinated populations.