Two babies in Kentucky have lost their lives to pertussis, also known as whooping cough, as recently reported by the Kentucky Department for Public Health. These deaths, the first pertussis-related since 2018, have refocused attention on a resurging danger once thought largely brought under control in America- vaccine-preventable illnesses.With over 10,000 cases reported across the country in the first six months of 2025, close to twice as many as the same six months a year ago public health officials are warning an alarm. The epidemic, which tracks with trends in other diseases like measles, coincides with declining childhood vaccination rates, anti-vaccination sentiment, and pandemic-period interruptions of routine vaccination activities.Whooping cough is a very contagious respiratory infection that is brought on by the bacterium Bordetella pertussis, originally described in 1906 by French scientists. Nevertheless, centuries ago, there were mentions of the illness—its earliest probable epidemic was seen in Paris in 1578.The disease is notorious for its intense, hacking cough that is followed by a piercingly high-pitched "whoop" upon inhalation. In newborns, particularly those too young to be vaccinated, pertussis may cause lethal complications such as pneumonia, seizures, and respiratory distress. Some doctors call it "the 100-day cough" because its duration lasts for many weeks or even months.According to the World Health Organization, pertussis still causes approximately 160,700 deaths annually in children under the age of five worldwide, a statistic that highlights the ongoing global burden of the disease, especially in settings with limited vaccine coverage.The two infants who perished in Kentucky in the last six months were not vaccinated, and neither were their mothers while pregnant. These events highlight a key gap in protection that maternal vaccination seeks to close. Babies under 6 weeks are too young to get their first dose of pertussis vaccine, and so remain extremely exposed early in life.Third-trimester maternal immunization allows for the passing on of protective antibodies to the newborn, protecting them until they are of age to start their own vaccine regimen. Without the added layer of protection, there is a marked increase in risk of severe illness or mortality.Through June 2025, the U.S. has reported a minimum of 8,485 confirmed cases of pertussis, already passing the 4,266 cases reported for the same period in 2024. For 2024, as reported by the CDC, a combined total of 35,435 cases were reported—more than five times that of 2023 and close to twice that of 2019, the final year before the pandemic.Kentucky alone has reported 247 cases of pertussis through 2025, after reporting 543 cases in 2024—the largest number in the state since 2012. Across the country, from October 2024 through April 2025, four deaths from pertussis have been reported: two infants, one school-age child, and one adult.Why Are Whooping Cough Cases Increasing Again?The return of pertussis in the United States is being fueled by a mix of related factors. One major cause is the cyclical pattern of the disease, since pertussis has epidemic patterns with episodes peaking every two to five years. Although such peaks are anticipated, experts note that the current peak is more severe compared to what is normally seen during normal peaks. Post-pandemic immunity gap is also a crucial factor. Throughout the COVID-19 pandemic that occurred during 2020 and 2022, pertussis rates decreased significantly because of widespread public health interventions like masking, physical distancing, and closing schools. Since those measures are no longer in effect, numerous persons including children who were left unvaccinated or were missed during their periodic vaccinations since then are now at increased risk for infection. Adding to this problem is the decrease in vaccination coverage, driven by increased misinformation, increased skepticism about the vaccine, and interruptions in access to health care. That decline in immunization, especially in infants and pregnant women, is one of the most urgent priorities driving the national epidemic of pertussis.How Effective Are Vaccines Against Pertussis?The pertussis vaccine itself has changed dramatically over the years since it was first introduced in the U.S. in 1914.Today's acellular form—DTaP for infants and children and Tdap for teens and adults—was introduced in the 1990s as a way to reduce side effects like seizures and high fevers that were caused by the older whole-cell vaccine. Although the acellular vaccine offers robust protection initially, the immunity fades with time. During the first year after completion of the five-dose course of childhood pertussis vaccination, some 98% of children are protected against pertussis. By the fifth year after the last dose, however, that immunity declines to roughly 65%. This drop highlights the necessity of booster shots in young adulthood and adolescence to ensure sustained protection. While immunity from the current vaccine is not long-term, it still represents the best weapon against severe disease, complications, and mortality. The unvaccinated are 13 times more likely to develop pertussis compared to their vaccinated counterparts, and they have much greater risks of being hospitalized or killed by the disease. Who Should Be Vaccinated, and When?The CDC and other top public health organizations suggest:Infants: Shots at 2, 4, and 6 months, with boosters at 15 months and 4 years.Adolescents: A Tdap booster dose at 11 or 12 years.Adults: One Tdap booster in adulthood, with re-vaccination every 10 years.Pregnant Women: One dose of Tdap between weeks 27–36 of every pregnancy to confer immunity to the newborn through passive antibody transfer.Local health departments might even suggest extra boosters for people who reside in outbreak-facilitating areas particularly on the West Coast, where states such as California, Washington, and Oregon have seen high case totals this year.How Can You Protect Yourself and Your Family?The increase in pertussis cases—and its disastrous effect on babies—underscores the necessity of public education, uniform messaging by health workers, and availability of immunization services. Parents and caregivers should be motivated to keep their own and children's vaccination schedules up to date, especially in communities where disease outbreaks are reported.Clinicians have a key role in advising maternal immunization and informing families about the signs of whooping cough, which is likely to be confused with the common cold at its initial onset.