Whooping cough in the United States

Whooping cough in the United States, medically known as pertussis, is a highly contagious respiratory disease caused primarily by the bacterium Bordetella pertussis. Pertussis remains a significant public-health concern due to cyclical outbreaks, waning immunity, and fluctuating vaccination rates.^[1] Although vaccines dramatically reduced incidence after the 1940s, the disease began its modern resurgence in the 1980s, after several decades of very low case numbers in the United States. This is supported by the U.S. Center for Disease Control and Prevention (CDC) surveillance data that reports “began increasing gradually” during that decade.^[2]

Cases have surged in the U.S. in 2024 and 2025, reaching levels not seen in years, with over 35,000 cases in 2024 and nearly 28,000 reported in 2025 by late December, significantly higher than only 7,000 in 2023. This resurgence follows a low in 2021 due to COVID-19 safety measures and is linked to declining vaccination rates, especially among children. ^[3]

About one in five children had vaccine-hesitant parents between 2019 and 2022, with increased hesitancy noted for Tdap in pregnant women by 2022–23.^[4] In Texas, around 85% of counties saw declines. The dropoff comes as several states are reporting significant increases in whooping cough.^[5]

The United States changed the whole-cell vaccine in the 1940s to the "acellular" kind in the 1990s, which has fewer side effects. The recommended vaccine went from DTP to DTaP. And when they did, the vaccine stopped protecting children as well as before. Recent studies show that protection against pertussis goes down 42% each year after the fifth vaccine dose, which is given at 4-6 years. This means that by the time kids get to be 10 or 11, they have hardly any protection at all. In 2010, when the first group of kids who had only gotten DTaP, not DTP, got to be about 10, there was an epidemic of pertussis in California. It was clear that we needed to boost protection. California made TdaP (the version of DTaP we give to older children and adults) mandatory in middle school, which helped for a while, but there was another epidemic in 2014.^[6] Teenagers in a study that were vaccinated with acellular pertussis (DTaP) in infancy were at a greater risk of developing pertussis than those vaccinated with whole-cell pertussis.^[7] To somewhat fix this problem of waning immunity, boosters for pertussis vaccines are recommended every 10 years.^[8]

Pertussis typically begins with mild cold-like symptoms before progressing to severe coughing fits that can last for weeks or months. The characteristic "whoop" sound occurs when patients inhale sharply after prolonged coughing. Infants under one year old facing the highest risk of severe outcomes, including death.^[9]