Whooping cough is surging across the United States, with multiple states recording their highest pertussis case counts in years. Washington state alone saw a 25-fold increase in cases in 2024 compared to 2023, and at least one person in the state died from the disease. Nationally, kindergarten vaccination coverage fell below 93 percent during the 2023-24 school year, a decline that public health officials say is leaving growing numbers of children vulnerable to a highly contagious bacterial infection that had been largely controlled for decades.
Falling vaccination rates and a fast-moving pathogen
The scale of the resurgence is not abstract. The Washington State Department of Health reported that pertussis cases jumped dramatically in 2024, documenting a roughly 25-fold increase over the prior year and confirming a pertussis-related death, a type of outcome that had become rare in the vaccine era. That single-state spike is among the sharpest documented anywhere in the country, but it is not isolated. Weekly provisional data published through the CDC’s infectious disease surveillance system show pertussis activity climbing across multiple jurisdictions after years of comparatively low numbers.
A key driver sits in the data on school-age children. A CDC analysis published in the Morbidity and Mortality Weekly Report found that nationwide kindergarten vaccination coverage dipped below 93 percent in the 2023-24 school year, with exemption rates continuing to inch upward. That threshold matters because pertussis spreads efficiently in close-contact settings like classrooms, and even modest drops in coverage can open gaps wide enough for outbreaks to take hold. When fewer children are vaccinated, chains of transmission can extend longer before they encounter someone who is protected, allowing a localized cluster to grow into a community-wide problem.
One hypothesis worth tracking is whether states with the largest recent increases in vaccine exemptions will show the steepest pertussis incidence rises in upcoming reporting quarters, independent of overall population vaccination coverage. The logic is straightforward: exemptions tend to cluster geographically, creating pockets of susceptibility that standard statewide coverage figures can mask. In a school where vaccination rates are high on paper but a handful of classrooms host most exempted students, a single introduction of pertussis can trigger an outsized outbreak. If that pattern holds, aggregate vaccination rates alone will not predict where the next surges hit hardest.
Immunity dynamics add another layer of vulnerability. The acellular pertussis vaccines used in the United States are highly effective at preventing severe disease in the short term, but protection against infection and mild illness wanes over several years. Children who received their full series on schedule can become susceptible again as adolescents if they miss recommended boosters. Adults, meanwhile, often have no recent vaccination and may experience milder, prolonged coughs that are never diagnosed as pertussis, silently spreading the bacterium to infants and other high-risk contacts.
How surveillance data confirm a multi-state pattern
The federal system for tracking pertussis relies on a standardized case definition published jointly by the CDC and the Council of State and Territorial Epidemiologists. That 2020 framework, outlined in the official pertussis case definition, specifies the clinical symptoms, laboratory criteria, and epidemiological links required to classify a case as confirmed or probable. Every state uses the same criteria when reporting to national systems, which means the rising numbers showing up in weekly provisional tables reflect a consistent measurement standard rather than a patchwork of local definitions.
The National Notifiable Diseases Surveillance System publishes jurisdiction-reported provisional case tables on a weekly basis, giving epidemiologists and the public a near-real-time view of disease activity. Archived weekly tables show pertussis counts accumulating across states well beyond the low baselines recorded during the height of the COVID-19 pandemic, when masking, school closures, and reduced travel suppressed many respiratory infections. The upward trend is appearing broadly, not confined to a single region or demographic group, and the pattern has persisted long enough to suggest more than a brief statistical fluctuation.
Pertussis is a cyclical disease that tends to peak every three to five years even in well-vaccinated populations, partly because immunity from both vaccination and natural infection wanes over time. Those cycles are visible in surveillance data stretching back decades. But the current surge is landing on top of declining childhood vaccination rates, which means the usual cyclical uptick is being amplified by a growing pool of susceptible individuals. Older adolescents and adults whose booster protection has faded add another layer of transmission risk, often carrying and spreading the bacterium before recognizing their own symptoms or seeking testing.
Public health departments are responding with a mix of targeted outreach and broader alerts. In some jurisdictions, health officials have urged clinicians to test more aggressively for pertussis in patients with persistent coughs, particularly when they have contact with infants, pregnant people, or immunocompromised individuals. School nurses and local health agencies are reviewing immunization records, identifying clusters of under-vaccinated students, and reminding families about state requirements for school entry. Where outbreaks have been confirmed, temporary exclusion policies for unvaccinated students and antibiotic prophylaxis for close contacts are being deployed to slow spread.
Gaps in the data and what to watch next
Several questions remain difficult to answer with the evidence currently available. State-specific weekly provisional counts for the most recent years have not been compiled into a single public table that allows clean year-over-year comparison across all reporting jurisdictions. That makes it hard to rank states by severity, quantify how much of the national increase is driven by a handful of hotspots, or test whether exemption increases correlate with incidence spikes at a granular level.
No published national analysis has yet addressed whether changes in testing volume or reporting practices since the updated case definition took effect are inflating apparent case counts. PCR testing for Bordetella pertussis has become more widely available, and awareness among clinicians may be higher in the wake of local alerts. Increased testing can surface cases that might have gone undiagnosed in earlier years, especially among adolescents and adults whose symptoms do not fit the classic “whooping” profile. Without an official accounting of testing trends alongside case trends, the precise contribution of better detection versus genuine increased transmission remains uncertain.
Age-stratified incidence data from weekly tables also remain limited in public summaries. That gap matters because the policy response differs depending on whether cases concentrate among under-vaccinated young children or among older age groups experiencing waning immunity. The first scenario calls for tighter enforcement of school-entry vaccination requirements, catch-up campaigns, and direct outreach to families in communities with high exemption rates. The second demands broader uptake of Tdap boosters among adolescents, adults, and especially pregnant people, who pass protective antibodies to their newborns.
For parents, the immediate questions are practical: how to reduce a child’s risk and when to worry about a cough. Health officials emphasize that the routine childhood vaccine series, followed by a Tdap booster at 11 or 12 years old and another dose during each pregnancy, remains the most effective tool for preventing severe disease and death. Families are encouraged to review their vaccination records with pediatricians, ask about catch-up schedules if doses were missed during the pandemic years, and pay attention to school notifications about pertussis exposures or immunization audits.
Clinicians, meanwhile, are being asked to keep pertussis on their diagnostic radar, particularly when they see prolonged coughs lasting more than two weeks, coughing fits followed by vomiting, or household clusters of illness. Early diagnosis allows for timely antibiotic treatment, which can shorten the infectious period and protect vulnerable contacts even if it does not fully eliminate symptoms. In communities where surveillance data show rising case counts, a lower threshold for testing and reporting can help health departments map transmission networks and target interventions where they are most needed.
The coming months will clarify whether the current surge represents the leading edge of a prolonged nationwide wave or a sharp but transient spike. As more detailed data become available, researchers will be watching for patterns that link local exemption policies, booster uptake, and demographic factors to the intensity of outbreaks. For now, the combination of falling vaccination coverage, waning immunity, and a pathogen primed to exploit close-contact settings has created conditions in which whooping cough can once again find footholds across the country-testing the resilience of a public health success story that many had assumed was safely in the past.
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*This article was researched with the help of AI, with human editors creating the final content.
