Whooping cough is more common than most people realize, and it’s been surging in recent years. The United States reported about 35,400 cases in 2024, a fivefold jump from the roughly 7,000 cases reported in 2023. Through the first months of 2025, nearly 29,000 cases had already been reported, suggesting another high-volume year.
Why Cases Are Rising Again
Whooping cough naturally moves in cycles, with outbreaks every three to five years regardless of vaccination rates. But the current wave is unusually large, and a key reason is the way modern vaccines work. The acellular pertussis vaccines used in the United States today don’t protect for as long as the older whole-cell vaccine that was phased out in the 1990s. Protection fades significantly within a few years of each dose.
For children who complete the full five-dose series, the vaccine is 98% effective in the first year after the last shot. Five years later, that drops to about 71%. The booster given to adolescents starts at roughly 73% effectiveness and falls to just 34% after four years. That steady decline means large portions of the population, especially older children, teens, and adults, are vulnerable between boosters. When a cyclical peak arrives, those gaps show up as sharp increases in reported cases.
Who Gets Whooping Cough Most Often
The disease doesn’t hit all age groups equally. Data from CDC surveillance shows that adolescents and adults account for nearly half of all cases. Between 2001 and 2003, the breakdown looked like this:
- Under 1 year old: 23% of cases
- Ages 1 to 4: 12%
- Ages 5 to 9: 9%
- Ages 10 to 19: 33%
- Over 20: 23%
The high proportion of teens and adults is partly a consequence of waning immunity. Many of these cases are milder and go undiagnosed for weeks, which is a problem because infected adults can easily spread the bacteria to infants who haven’t yet been fully vaccinated.
Infants Face the Greatest Danger
While teens and adults make up the largest share of total cases, infants bear the worst outcomes by far. Babies younger than six months account for 10 to 15% of all whooping cough cases, yet more than 90% of all deaths from the disease occur in this age group. Their airways are small, their immune systems are immature, and they haven’t received enough vaccine doses to build meaningful protection.
Vaccination during pregnancy is one of the most effective tools for closing this gap. When a pregnant person receives a booster during the third trimester, the antibodies that cross the placenta prevent about 78% of whooping cough cases in newborns under two months old and reduce hospitalizations in that age group by roughly 90%.
Recent Outbreaks Across the U.S.
The 2024 and 2025 surge hasn’t been evenly distributed. Texas reported more than 3,500 cases through October 2025, roughly four times the number for the same period the previous year. Several other states have issued similar health alerts, consistent with the expected pattern of a cyclical peak amplified by waning population immunity.
These surges tend to concentrate in schools and communities where large groups of similarly aged people spend time together indoors. Because the bacteria spread through respiratory droplets from coughing and sneezing, close and prolonged contact increases transmission. A single infected person in a household will typically spread whooping cough to most unvaccinated family members.
How Underreporting Skews the Numbers
Official case counts almost certainly underestimate the true burden of whooping cough. In adults, the infection often presents as a persistent cough lasting weeks rather than the dramatic “whoop” sound associated with the disease in children. Many adults never seek medical care, and even those who do may not be tested for pertussis. Public health experts have long noted that reported cases represent only a fraction of actual infections, particularly among adults whose symptoms mimic bronchitis or a lingering cold.
So when the CDC reports 35,000 cases in a year, the real number of infections circulating in the population is likely several times higher. This matters for anyone living with or caring for a young infant, because the source of a baby’s infection is usually a household member who doesn’t know they’re carrying the bacteria.