Pertussis is a bacterial respiratory infection caused by Bordetella pertussis, and the people who suffer most from it are babies under 6 months old. CDC's preliminary 2024 surveillance data shows 35,435 US pertussis cases, a sharp jump from the 7,063 cases in 2023 and roughly six times the average of the previous five years. Most reported cases are in adolescents and adults whose vaccine protection has worn off, but most hospitalizations and deaths are in infants who haven't completed their primary series yet.

Whooping cough has a public-relations problem. People hear "vaccine-preventable" and assume it's gone. It's not. The current acellular pertussis vaccines protect well against severe disease, but immunity wanes faster than the older whole-cell vaccines that were phased out in the 1990s. The math is now playing out as cyclical surges every 3 to 5 years, with 2024 being one of the worst US years since the 1950s. Pertussis is part of the broader infection prevention picture that includes masks, hand hygiene, and household isolation during illness.

Key Takeaways

What is pertussis and why is it surging?

Pertussis is a respiratory infection caused by Bordetella pertussis bacteria that triggers prolonged, paroxysmal coughing fits. US cases surged to 35,435 in 2024 from 7,063 in 2023, the highest count since 2014, driven by waning vaccine-induced immunity, the 2020-2022 collapse in routine childhood immunization, and the cyclical 3-to-5-year peaks built into pertussis epidemiology.

The acellular pertussis vaccine introduced in the 1990s replaced the older whole-cell vaccine because it caused fewer side effects. The trade-off was shorter-lived protection. Effectiveness drops to roughly 70% by 1 year after the fifth childhood dose and continues falling. Adults who got their last DTaP at age 11 may have minimal residual protection by their 30s.

COVID-era drops in routine vaccinations created a cohort of children with incomplete primary series, and that population is now driving school-based outbreaks. Australia, the UK, China, and most of continental Europe saw similar surges in 2024-2025. Our vaccine efficacy explained post covers why some vaccines need boosting and others don't.

How does whooping cough sound different from a regular cough?

The hallmark is a paroxysm: a fast burst of 5 to 15 short coughs back-to-back without inhaling between them, followed by a deep, sharp inhaled "whoop" as the patient finally pulls air in past swollen airways. Adults often skip the whoop and just have a brutal, lingering cough that worsens in fits, sometimes ending in vomiting or fainting from oxygen debt.

Pertussis cough is dry, exhausting, and worse at night. Coughing fits last 1 to 2 minutes and recur dozens of times a day during the paroxysmal phase. People describe being unable to catch their breath until the fit ends. Between fits, patients can look completely well, which is part of why physicians who haven't seen pertussis miss it.

Infants under 6 months often don't cough at all. Instead they have apnea (pauses in breathing), cyanosis (turning blue), and exhaustion. Any baby that goes blue or stops breathing during what looks like a cold is a medical emergency. Pertussis testing in babies with apnea catches a meaningful fraction of cases that would otherwise be misattributed.

How is pertussis transmitted?

Pertussis spreads through respiratory droplets from coughs, sneezes, and close conversation. The basic reproduction number is 12 to 17, which puts it in the same range as measles and far above seasonal flu. People are contagious from the start of cold-like symptoms through 3 weeks of coughing, or 5 days after starting appropriate antibiotics, whichever comes first.

That high transmissibility plus the long incubation period (5 to 10 days, sometimes up to 21) means pertussis quietly seeds households and classrooms before anyone realizes what they have. Adults with the "cough that won't quit" are common index cases for infant infections at home, which is the central reason adolescent and adult Tdap boosters exist.

Standard household precautions during a confirmed pertussis case: well-fitted masks for everyone except the patient when sharing rooms, separate sleeping areas if possible, and antibiotic post-exposure prophylaxis for close contacts under physician guidance. The home isolation guide has the room-by-room protocol that applies here too.

When should adults get a Tdap booster?

CDC recommends a single Tdap dose at age 11 or 12, then a Td or Tdap booster every 10 years for adults. Pregnant people should receive Tdap during every pregnancy at 27 to 36 weeks gestation, regardless of when their last booster was. Adults who will be in close contact with a newborn and haven't had a Tdap as an adult should get one at least 2 weeks before contact.

Healthcare workers, childcare staff, and anyone working with infants are the standing exceptions where Tdap is given regardless of the 10-year interval. After a deep wound or potentially contaminated injury, a Tdap is given if the last tetanus booster was more than 5 years ago, which is a useful opportunity for adults overdue on pertussis coverage.

The 78% protective figure from maternal Tdap comes from a CDC case-control study published in Clinical Infectious Diseases in 2017, looking at babies under 2 months hospitalized with pertussis. The maternal antibody crosses the placenta and gives the infant passive immunity through the months when they are too young for their own vaccine doses.

How do you protect newborns who can't be vaccinated yet?

The cocoon strategy: vaccinate everyone who will be in close contact with a newborn. Parents, grandparents, siblings over 11, nannies, and visiting relatives should all be current on Tdap, ideally at least 2 weeks before any contact. Combine cocooning with maternal Tdap during pregnancy and you cover both passive infant immunity and the most likely transmission paths.

First DTaP dose is given at 2 months, with subsequent doses at 4 months, 6 months, 15 to 18 months, and 4 to 6 years. Babies are most vulnerable in the window between birth and the third dose at 6 months, when their own immunity is partial. Maternal Tdap is the critical bridge for the first 2 to 3 months of life.

If pertussis is circulating in your area and you have a newborn, mask in public, ask sick visitors to stay away, and consider postponing daycare onset for the youngest babies. Most pertussis deaths in the US are in babies under 3 months, which is why the prevention strategy concentrates so heavily on that single window.

FAQ

How long does whooping cough last?

The full course runs 6 to 10 weeks, sometimes longer in adults. The catarrhal phase (cold-like symptoms) lasts 1 to 2 weeks, the paroxysmal phase with the violent coughing fits lasts 2 to 6 weeks, and the convalescent phase of fading cough lasts another 2 to 6 weeks. The "100-day cough" name reflects how long residual cough persists after the bacteria are gone.

Will antibiotics shorten whooping cough?

If started in the first 1 to 2 weeks, macrolide antibiotics (azithromycin, clarithromycin, erythromycin) can shorten the illness and reduce contagiousness. Started later, they don't change the cough but still prevent further transmission. Treatment is recommended for all confirmed cases and for high-risk close contacts as post-exposure prophylaxis, even if asymptomatic.

Can you get pertussis if you've been vaccinated?

Yes. Acellular pertussis vaccine effectiveness wanes within 5 to 10 years. Vaccinated people who get pertussis usually have milder disease and a shorter contagious period than unvaccinated people, but they can still spread it. This is why population-level pertussis control depends on consistent boosting plus high primary-series coverage in children.

How do doctors test for pertussis?

PCR on a nasopharyngeal swab is the standard test, with highest sensitivity in the first 3 weeks of cough. Bacterial culture has high specificity but slow turnaround. Serology can help in later disease but is less standardized. Many cases are diagnosed clinically when classic symptoms appear during a known outbreak, with PCR used for confirmation and contact-tracing decisions.

Is the Tdap shot the same as a tetanus shot?

Tdap covers tetanus, diphtheria, and acellular pertussis in one shot. Td is just tetanus and diphtheria. Adults due for a tetanus booster after age 19 can get Tdap at the next opportunity to refresh pertussis coverage too. After that, the standard 10-year tetanus booster can be Td or Tdap depending on availability and clinician preference.