{"id":83022,"date":"2026-04-21T01:16:17","date_gmt":"2026-04-21T01:16:17","guid":{"rendered":"https:\/\/christiancorner.us\/index.php\/2026\/04\/21\/why-japan-sees-a-big-increase-in-pertussis-in-2025-while-other-countries-peaked-earlier\/"},"modified":"2026-04-21T01:16:58","modified_gmt":"2026-04-21T01:16:58","slug":"why-japan-sees-a-big-increase-in-pertussis-in-2025-while-other-countries-peaked-earlier","status":"publish","type":"post","link":"https:\/\/christiancorner.us\/index.php\/2026\/04\/21\/why-japan-sees-a-big-increase-in-pertussis-in-2025-while-other-countries-peaked-earlier\/","title":{"rendered":"Why Japan sees a big increase in pertussis in 2025, while other countries peaked earlier"},"content":{"rendered":"

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Pertussis cases declined during the pandemic, then increased again in many countries, but a delayed outbreak in Japan in 2025 stands out because of its scale and its heavy impact on older children and adolescents. The findings raise new questions about waning immunity, booster policy and how best to protect infants in the post-pandemic era.<\/strong><\/em><\/span><\/p>\n

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Study: Resurgence of pertussis following COVID-19 pandemic in four Western Pacific countries and the United States, highlights 2025 outbreak in Japan<\/a>. Image Credit: Katrina Cone\/Shutterstock<\/em><\/span><\/p>\n

In a recent study published in the journal scientific report<\/cite><\/strong><\/a>A group of researchers analyzed post-coronavirus disease 2019 (COVID-19<\/abbr>) Resurgence patterns of pertussis in several countries, with a focus on Japan’s unique 2025 outbreak.<\/p>\n

Pertussis risk, waning immunity, and post-pandemic changes<\/h2>\n

What happens when pandemic precautions disappear, and do old diseases become strong again? Global public health systems and vaccination strategies control infectious diseases such as pertussis (whooping cough) that were once common and vaccine-preventable.<\/p>\n

during COVID-19<\/abbr> During the pandemic, strict public health measures reduced the spread of infectious diseases, but once these restrictions were lifted, many countries reported a sharp increase in cases of whooping cough.<\/p>\n

Weakened immunity, combined with low booster vaccination rates and evolving bacterial resistance, has made pertussis more challenging to control. Infants are most at risk; However, the increasing incidence of pertussis in adolescents and adults raises new concerns about transmission dynamics. <\/p>\n

Continued research is necessary to explore the changing epidemiological patterns associated with pertussis and develop effective prevention strategies.<\/p>\n

Multi-Country Pertussis Surveillance Study Design<\/h2>\n

The present retrospective study used publicly available national pertussis surveillance data from Japan, Australia, New Zealand, China, and the United States (usa<\/abbr>).<\/p>\n

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Data were collected from various official public health databases, including the Japan Health Protection Institute, the Centers for Disease Control and Prevention, and other national surveillance systems. The study period extended from 2018 to July 2025, allowing comparison of the period before, during and after government restrictions.<\/p>\n

Annual and monthly case counts were extracted and used to calculate incidence rates per 100,000 population.<\/p>\n

For countries lacking direct monthly data, weekly reports were collected. Age-specific incidence rates and case proportions were analyzed to identify demographic trends, particularly among adolescents and infants. Geographic distribution was examined at subnational levels using incidence-mapping tools.<\/p>\n

Temporal changes were evaluated using three different stages of analysis: pre-COVID-19<\/abbr> (2018-2019), pandemic restrictions phase (2020-2022), and post-restrictions phase (2023-2025). Statistical comparisons were performed using non-parametric tests due to non-normal data distribution.<\/p>\n

The researchers used time-series analysis with segmented regression models to evaluate how changes to pandemic measures affected infection trends from 2023 and measured these changes using rate ratios. Ethical approval was not required, as all data were anonymized and publicly available.<\/p>\n

Japan’s 2025 outbreak and age-change findings<\/h2>\n

In all five countries, cases of whooping cough declined sharply during COVID-19<\/abbr> The pandemic (2020\u20132022), social distancing, masking, and reduced mobility showed an impact, but this suppression was temporary. When restrictions were lifted, there was a resurgence, with a significant increase in incidence seen in all countries during 2023\u20132025.<\/p>\n

Statistical analysis showed that the incidence of pertussis increased significantly after the phase out of epidemic preventive measures in all five countries, although the study was descriptive and did not prove a single cause of the rebound.<\/p>\n

Australia, New Zealand, China, and the United States recorded the highest incidence of pertussis in 2024, with Australia recording the highest incidence of more than 200 cases per 100,000.<\/p>\n

The outbreak occurred late in Japan compared to other countries; While other countries began to decline after their peak, Japan saw a dramatic increase in the number of cases (60,826 by July 31, 2025, based on a partial-year count), more than ten times the number reported in 2024.<\/p>\n

This delayed outbreak may reflect a gradual accumulation of susceptible individuals rather than an immediate rebound, although the authors noted that differences in surveillance systems, vaccination coverage, and other factors may also have contributed.<\/p>\n

The age distribution by disease category has changed dramatically from previous records. In the past, the incidence rate of the disease was highest among infants. However, with the recent pandemic, the incidence of the disease has increased in adolescents and school-aged children. In Japan in 2025, children aged 10\u201319 accounted for more than 50% of all cases, and the incidence rate reached 270\/100,000 population.<\/p>\n

Emerging trends suggest that immunity from childhood vaccination is waning and there are barriers to taking a booster vaccine.<\/p>\n

Geographically, distinct patterns emerged. In Japan and New Zealand, higher incidence rates were seen in non-metropolitan areas, suggesting a possible link to differences in population structure, health care access or vaccination coverage.<\/p>\n

In contrast, Australia’s outbreak was concentrated in densely populated states, while the United States showed a mixed pattern across different regions.<\/p>\n

Immunization coverage for primary childhood vaccination remained high in all countries, often exceeding 90%. However, booster vaccination strategies varied considerably. Countries with regular teen boosters showed different outbreak patterns, while Japan experienced a more pronounced increase among teenagers.<\/p>\n

Because vaccination data was ecological, however, the study could not confirm protection gaps at the individual level or prove that booster policy differences directly caused the observed outbreaks.<\/p>\n

Death rates remained relatively low but remain a matter of concern, particularly among vulnerable populations. Infants continue to suffer serious outcomes, and deaths have also been reported in older age groups, indicating that pertussis remains a threat throughout life.<\/p>\n

Booster vaccination and public health implications<\/h2>\n

Resurgence of pertussis after COVID-19<\/abbr> The pandemic reflects the unintended consequences of disrupted immunity and changing public health dynamics. While most countries experienced an early resurgence, Japan’s unique experience highlights significant concerns associated with the absence of government-funded routine pertussis boosters for adolescents and preschool children. Additionally, this variation in the age of individuals infected with pertussis has serious implications for ongoing transmission and child protection.<\/p>\n

The findings support consideration of routine booster vaccines and vaccination during pregnancy as potential strategies to reduce future risk, rather than proving that these measures alone will prevent future outbreaks. These findings highlight the need for adaptive, evidence-based public health policies to address growing infectious disease threats in a post-pandemic world.<\/p>\n

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Journal Reference:<\/p>\n

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