Pertussis resurgence after the COVID-19 pandemic in four Western Pacific Countries and the USA, highlighting the 2025 outbreak in Japan

Pertussis is a re-emerging, highly contagious respiratory disease posing a significant public health challenge globally. This retrospective study characterized the divergent pertussis resurgence after the coronavirus-disease-2019 (COVID-19) pandemic by analyzing national surveillance data from four countries of the Western Pacific region (Japan, Australia, New Zealand, China) and the United States of America, with a focus on characterizing the unique outbreak in Japan. A significant outbreak began relatively late in Japan in 2025; as of July 31, 2025 (a 7 month partial count, potentially underestimated), the country had recorded 60,826 cases (incidence rate 49.13/100,000 population), substantially exceeding the 4054 cases of the previous year. This surge stands in contrast to the earlier 2024 peaks and subsequent decreases in the other four study countries. All five countries experienced a significant increase in cases between the preventive measures phases of the COVID-19 (2020-2022) and the loosening of these measures (2023-2025) (p < 0.001). Japan's 2025 resurgence was characterized by high incidence among individuals aged 5-19 years, particularly adolescents (56.6% of cases), and concentrated in non-metropolitan prefectures. This resurgence, which may be linked to the lack of routine booster vaccinations, highlights the need to re-evaluate national immunization strategies to control the evolving threat of pertussis.