Global Pertussis Resurgence: Understanding Japan’s 2025 Surge

Japan experienced a significant surge in pertussis cases in 2025, with over 28,000 reported infections nationwide — a sharp increase from fewer than 5,000 cases in 2024 — according to data released by the National Institute of Infectious Diseases (NIID) in Tokyo. This resurgence stands in contrast to trends in many other high-income countries, where pertussis activity peaked earlier, during or shortly after the COVID-19 pandemic, and has since declined or stabilized at lower levels.

Pertussis, also known as whooping cough, is a highly contagious bacterial respiratory infection caused by Bordetella pertussis. It is characterized by prolonged coughing fits that can last for weeks or months, posing particular risks to infants too young to be fully vaccinated and to individuals with waning immunity. While routine childhood vaccination programs have long kept pertussis under control in many countries, immunity from both natural infection and acellular pertussis vaccines (such as DTaP and Tdap) is known to decrease over time, typically within 4 to 12 years after the last dose.

Experts suggest that Japan’s delayed pertussis peak may be linked to a combination of factors, including exceptionally low transmission during the pandemic years due to strict public health measures such as mask-wearing, school closures, and reduced social mixing. These interventions suppressed not only SARS-CoV-2 but also other respiratory pathogens, including pertussis. A larger-than-usual proportion of the population — particularly adolescents and young adults — remained susceptible to infection when restrictions eased and normal social interactions resumed in 2023 and 2024.