Infants under one year old have the highest rate of whooping cough of any age group, with a reported incidence of about 23 per 100,000 infants in 2023. That number climbed sharply in 2024, when reported cases across the United States increased more than sixfold compared to the previous year. While still relatively uncommon in absolute terms, whooping cough hits this age group harder than any other, carrying the greatest risk of hospitalization and death.
Why Infants Are the Most Affected Age Group
Babies are vulnerable to whooping cough because their immune systems are still developing and they haven’t yet completed their vaccine series. The first dose of the childhood pertussis vaccine isn’t given until two months of age, and full protection requires multiple doses over the first year and beyond. That leaves a window, especially in the first few months of life, where infants have little to no immunity of their own.
This vulnerability shows up clearly in hospitalization data. Among all whooping cough hospitalizations in children under two years old during a ten-year CDC study period, 92% occurred in babies younger than six months. These very young infants often need hospital care for coughing spells so severe they interfere with breathing and feeding.
Recent Trends in the U.S.
Whooping cough cases dropped dramatically during the early pandemic years, likely due to masking, social distancing, and reduced contact between people. That changed in 2024, when cases surged nationwide. Preliminary CDC data show more than six times as many cases were reported in 2024 compared to 2023. Cases peaked around November 2024 and have been trending down since, but numbers remain elevated compared to pre-pandemic levels.
Globally, the World Health Organization reported more than 151,000 cases of whooping cough in 2018, though the true number is thought to be much higher due to underdiagnosis. The disease remains a significant cause of illness and death in infants worldwide, particularly in regions with lower vaccination coverage.
Symptoms Look Different in Babies
One of the most important things to understand about whooping cough in infants is that it often doesn’t look like whooping cough. The disease gets its name from the gasping “whoop” sound older children and adults make after a coughing fit, but many babies never develop that characteristic cough at all.
Instead, the most concerning symptom in young infants is apnea: life-threatening pauses in breathing. During these episodes, a baby may turn blue (a sign called cyanosis) or visibly struggle to breathe. This is part of what makes the disease so dangerous in this age group. Parents expecting a dramatic cough may not recognize the early signs, and the breathing pauses themselves can be fatal.
Complications in Young Infants
When whooping cough does become severe, the complications can be serious. Pneumonia is the most common, developing when the infection spreads deeper into the lungs or when a secondary bacterial infection takes hold. Seizures and a dangerous brain condition called encephalopathy can also occur, caused by oxygen deprivation during prolonged coughing or breathing episodes. In the most severe cases, whooping cough is fatal, and nearly all deaths occur in infants, particularly those under six months.
Infants who are hospitalized typically need supportive care: monitoring of breathing, help with feeding, suctioning of mucus, and sometimes supplemental oxygen. Recovery can take weeks, and the cough (when present) may linger for months, which is why whooping cough was historically called the “100-day cough.”
How Maternal Vaccination Protects Newborns
Because babies can’t receive their own vaccine until two months old, one of the most effective strategies for protecting newborns is vaccination during pregnancy. When a pregnant person receives the Tdap vaccine between 27 and 36 weeks of pregnancy, their body produces antibodies that cross the placenta and provide the baby with temporary protection after birth. This approach lowers the risk of whooping cough in babies younger than two months by 78%.
That protection is especially critical during the first weeks of life, when infants are most vulnerable and least able to fight the infection on their own. The antibodies from maternal vaccination gradually fade, which is why the infant’s own vaccine series, starting at two months, is essential for continued protection. As of 2018, about 86% of infants globally had received the recommended three-dose series.
How Whooping Cough Is Diagnosed
Diagnosing whooping cough in infants can be tricky because the symptoms overlap with other respiratory illnesses, especially in the early stages when it resembles a mild cold. The gold standard for confirmation is a bacterial culture taken from a nasal swab, which is the only method that’s 100% specific for the pertussis bacteria. However, cultures need to be collected within the first two weeks of cough onset, while the bacteria are still present, which limits their usefulness if diagnosis is delayed.
A faster molecular test (PCR) is also widely used and can detect genetic material from the bacteria even when a culture might come back negative. In practice, doctors often start treatment based on symptoms and exposure history rather than waiting for lab confirmation, since early antibiotic treatment reduces severity and limits spread to other vulnerable contacts.