Abstract
Objectives
Since 2024, the number of pertussis cases in the Republic of Korea has rapidly increased, resulting in a nationwide outbreak. We analyzed the epidemiological characteristics and trends associated with this foutbreak, examined its potential causes, and described the public health responses implemented to date, to provide foundational evidence to inform future policy development.
Methods
Data were obtained from January 2024 to June 2025, and included case notifications from the surveillance and immunization systems of the Korea Disease Control and Prevention Agency, individual case investigation forms, and outbreak reports. Descriptive statistics were used to analyze patient age, regional distribution, clinical symptoms, outbreak status, and vaccination status.
Results
From January 2024 to June 2025, a total of 52,651 pertussis cases were reported: 5,497 in the first half of 2024, 42,551 in the second half of 2024, and 4,603 in the first half of 2025. The incidence peaked in July 2024, declined briefly, then increased again in November before gradually decreasing in 2025. School-aged children and infants under one year of age accounted for 84.6% and 0.3% of cases, respectively. One death was reported. In 2024, 30.5% of reported cases were linked to outbreak clusters, most of which occurred in schools (97%).
Conclusions
The 2024 outbreak affected school-aged children and adolescents, highlighting the need for stronger community surveillance. To protect high-risk groups including infants and pregnant women, vaccination coverage must be increased. Ongoing monitoring of resistant strains and related species, and sustained interagency collaboration are essential.
Keywords: Pertussis, Public health surveillance, Vaccination, Disease outbreaks
Key messages
① What is known previously?
In the Republic of Korea, pertussis incidence has remained low due to high vaccination coverage, but outbreaks recur every three to five years.
② What new information is presented?
In contrast to past patterns that showed higher proportions among children and adults, the 2024 outbreak was characterized by a nationwide surge among school-aged adolescents, with persistent small-scale clusters reported in school.
③ What are implications?
Coordinated interagency rapid response and vaccination and preparedness strategies for high-risk groups including infants under 1 year of age and pregnant women must be strengthened to prevent early school transmission.
Introduction
Pertussis is an acute respiratory infectious disease caused by Bordetella pertussis that poses risks of severe complications and mortality, particularly among infants and young children who have not completed their vaccinations [1]. In the Republic of Korea (ROK), pertussis was classified as a notifiable disease under the Infectious Disease Control and Prevention Act, which was enacted in 1957. The introduction of the diphtheria-tetanus-whole cell pertussis (DTwP) vaccine in 1958, followed by the enhanced diphtheria-tetanus-acellular pertussis (DTaP) vaccine in 1982, has resulted in vaccination rates exceeding 90%. This high vaccination coverage has led to a substantial decline in both the incidence and mortality rates associated with pertussis [2]. Consequently, vaccination rates have remained elevated, sustaining the overall low incidence of the disease. Nevertheless, sporadic outbreaks have been reported in various regions [2]. Even in countries with high vaccination rates, such as those in Europe and Australia, periodic outbreaks of pertussis occurring every 2 to 5 years have been consistently documented. Notably, in 2024, an unusually large-scale outbreak emerged globally [3].
In nations such as China and the United States, several key factors have been implicated in the recent outbreak. A notable waning immunity conferred by the acellular pertussis (aP) vaccine has been observed. Additionally, an “immunity debt” appears to have arisen due to the lack of natural infection opportunities during the coronavirus disease 2019 (COVID-19) pandemic. Changes in the genotypes of B. pertussis, particularly the proliferation of the ptxP3 lineage, have also been documented. Furthermore, the emergence and spread of macrolide-resistant B. pertussis have been identified, alongside a decrease in vaccination rates attributed to increased vaccine refusals and delays in immunization [4-7]. These trends are particularly concerning in light of the recent surge in confirmed cases, which has coincided with a notable rise in the prevalence of strains exhibiting antimicrobial resistance and vaccine evasion capabilities. Reports of reinfection have also emerged among individuals who have completed their vaccinations [5,6].
In ROK, a small-scale outbreak originating in schools in Gyeongsangnam-do during the latter half of 2023 extended into early 2024. This outbreak subsequently propagated nationwide, with numerous cases primarily affecting school-age children and adolescents aged 7–18 years. This study aimed to systematically organize data regarding the incidence of pertussis by age and region, analyze clinical symptoms and vaccination history, and evaluate public health measures based on reported cases from January 1, 2024, to June 30, 2025. The findings are intended to provide foundational data for the formulation of effective response strategies aimed at protecting high-risk groups and preventing community transmission in the future.
Methods
1. Data Source
Data prior to 2024 were obtained from case reports submitted through the Integrated Disease and Health Management System. Data from 2024 onward were analyzed based on pertussis case documents reported through the Integrated Disease Control Information System of the Korea Disease Control and Prevention Agency (KDCA) within a comprehensive surveillance framework. The analysis encompassed all reported cases, including suspected cases, from January 1, 2024, to June 30, 2025, based on the reporting date. Epidemiological information was extracted from the patient’s epidemiological investigation report. The analysis of vaccination history was facilitated by linking data recorded in the Integrated Vaccination Management System, which verified the latest vaccination status. Epidemiological investigation data were collected and validated by compiling information submitted as “pertussis” to the outbreak management system within the Integrated Disease Control Information System throughout 2024.
2. Definition
In accordance with the diagnostic criteria for pertussis reporting established in the “Integrated Guidelines for Diagnostic Testing of Statutory Infectious Diseases” provided by the KDCA, a confirmed case is defined as an individual exhibiting clinical symptoms consistent with pertussis (e.g., a runny nose, sneezing, low-grade fever, paroxysmal cough, and vomiting following coughing) who also meets the infection confirmation criteria through diagnostic testing. Individuals suspected of having pertussis based on clinical symptoms and epidemiological associations but lacking test results that satisfy the diagnostic criteria were classified as suspected cases [8]. The total number of reported cases was calculated by aggregating the number of patients who met the established reporting criteria along with suspected cases.
The vaccination history of confirmed and suspected cases was categorized according to the latest vaccination status from the first to sixth doses for each age group. The completion status of previous doses prior to the latest vaccination history for each age group was not accounted for. However, cases in which pertussis was confirmed within 14 days following vaccination were excluded from being classified as completed for that dose, due to the time required for antibody formation. Following the transition of the National Childhood Vaccination Support Program to a fully fee-free status in 2014, the systematic documentation and reporting of all vaccination records through the Integrated Vaccination Management System has been mandated. This system is utilized for the purpose of processing cost reimbursement claims [9]. Consequently, any subsequent vaccinations are assumed to have been registered. Accordingly, cases with no vaccination history prior to 2014 were categorized as “unknown,” while cases with no vaccination history after 2014 were classified as “unvaccinated.” Infants under 2 months of age who had not yet reached the recommended vaccination age and had no vaccination history were also classified as “unvaccinated.”
3. Analysis Methods
The quantitative analysis focused on incidence rates by sex, age, and case classification; clinical characteristics; regional incidence counts; cumulative incidence per 100,000 population; vaccination status; and the status of epidemiological investigations into outbreaks. This analysis was based on domestic pertussis incidence trends over the past decade from 2016 to 2025, as well as reported cases and epidemiological investigation records from January 1, 2024, to June 30, 2025. The collected case reports and epidemiological investigation records were analyzed using Microsoft Excel 2021 (Microsoft Corporation), with an emphasis on descriptive statistics.
Results
1. Pertussis Report Status
Over the past decade, domestic pertussis cases have consistently remained below 1,000 annually, with small-scale outbreaks occurring every 2 to 5 years. However, during the COVID-19 pandemic, reported cases decreased to fewer than 100 annually. A resurgence of cases began in the latter half of 2023, primarily due to outbreaks in educational institutions. In 2024, the total number of reported cases escalated to 48,048, representing the most significant outbreak since the establishment of the domestic infectious disease surveillance system. A review of monthly trends reveals a peak of 10,586 cases in July 2024, followed by a decline to 3,623 cases in September. Nevertheless, a resurgence occurred in October, with a peak of 9,683 cases recorded in November, after which a downward trend resumed. By January 2025, 2,296 cases were reported, with a decline to fewer than 1,000 cases per month beginning in February. As of June 30, 2025, a total of 4,603 cases had been reported in the first half of the year (Table 1).
Table 1. Reported confirmed and suspected cases of pertussis in the past 10 years (2016–2025).
| 2016 | 2017 | 2018 | 2019 | 2020 | 2021 | 2022 | 2023 | 2024 | 2025 (as of June 30) |
|
|---|---|---|---|---|---|---|---|---|---|---|
| Total | 129 | 318 | 980 | 496 | 123 | 21 | 31 | 292 | 48,048 | 4,603 |
| Confirmed case | 123 | 104 | 796 | 346 | 122 | 15 | 27 | 276 | 47,786 | 4,581 |
| Suspected case | 6 | 214 | 184 | 150 | 1 | 6 | 4 | 16 | 262 | 22 |
From January 1, 2024, to June 30, 2025, the total number of reported pertussis cases reached 52,651, with confirmed cases comprising 99.5% and suspected cases representing 0.5%. The number of cases sharply increased from 5,497 in the first half of 2024 to 42,551 in the second half before declining to 4,603 in the first half of 2025, reverting to levels seen in the first half of 2024.
By sex, males accounted for 57.6% of the cases, while females comprised 42.4%, establishing a male majority. The proportion of males exhibited a consistent upward trend, increasing in every half-year period. Notably, in the first half of 2024, the sex difference was pronounced, with males constituting 65.6% and females 34.4%. By age group, 84.6% of reported cases occurred in school-age individuals aged 7–18 years. In the first half of 2024, middle and high school students (ages 13–18 years) accounted for 60.0%, followed by a decline in the second half, dropping to 28.0% in the first half of 2025, a decrease of more than half. Conversely, the proportion of elementary school students (ages 7–12 years) increased from 31.6% in the first half of 2024 to 46.4% in the second half. Despite a slight decline to 39.7% in the initial half of 2025, this age group remained the largest proportion, accounting for 44.3% of all reported cases (Table 2). In the first half of 2024, adults aged ≥19 years accounted for 6.7% (366 individuals) of the population, but this proportion rose to 10.6% (4,511 individuals) in the second half of the year. This upward trend continued, reaching 26.2% (1,206 individuals) in 2025, indicating the most significant growth rate between the first half of 2024 and the first half of 2025. Infants under 1 year of age, who are at high risk of severe illness and death, accounted for 0.2% (108 cases) of all reported cases in 2024 and 0.7% (31 cases) in the first half of 2025. Notably, in 2024, a single related fatality was documented in an infant under 2 months of age who had not yet reached the age for vaccination.
Table 2. General characteristics of confirmed and suspected pertussis cases, from 2024 to the first half of 2025.
| Category | Total | First half of 2024 | Second half of 2024 | First half of 2025 |
|---|---|---|---|---|
| Total | 52,651 (100.0) | 5,497 (100.0) | 42,551 (100.0) | 4,603 (100.0) |
| Sex | ||||
| Male | 30,331 (57.6) | 3,606 (65.6) | 24,410 (57.4) | 2,315 (50.3) |
| Female | 22,320 (42.4) | 1,891 (34.4) | 18,141 (42.6) | 2,288 (49.7) |
| Age (yr) | ||||
| 0 | 139 (0.3) | 6 (0.1) | 102 (0.2) | 31 (0.7) |
| 1–6 | 1,895 (3.6) | 89 (1.6) | 1,558 (3.7) | 248 (5.4) |
| 7–12 | 23,330 (44.3) | 1,738 (31.6) | 19,763 (46.4) | 1,829 (39.7) |
| 13–18 | 21,204 (40.3) | 3,298 (60.0) | 16,617 (39.1) | 1,289 (28.0) |
| ≥19 | 6,083 (11.6) | 366 (6.7) | 4,511 (10.6) | 1,206 (26.2) |
| Case classification | ||||
| Suspected case | 284 (0.5) | 72 (1.3) | 190 (0.4) | 22 (0.5) |
| Confirmed case | 52,367 (99.5) | 5,425 (98.7) | 42,361 (99.6) | 4,581 (99.5) |
Unit: case (%).
2. Epidemiological Characteristics of All Pertussis Patients in 2024
In 2024, the total number of reported pertussis cases was 48,048, of which 47,637 cases (99.1%) with available clinical symptom information were included in the analysis. The predominant clinical symptom was cough, observed in 99.8% of all patients. Among these, paroxysmal coughing was reported in 15.4% (7,336 cases), while whooping (a “whoop” sound heard during inhalation) was present in 12.3% (5,842 cases). Dyspnea and vomiting were reported in 1.2% (581 cases) and 3.0% (1,406 cases), respectively.
A hospitalization history was identified in 11.5% (5,500 cases) of the total, with 0.2% of these cases confirmed to have been admitted to the intensive care unit (ICU). Age-specific hospitalization rates were highest for individuals aged 0 years at 47.2% (51 cases) and for those aged ≥65 years at 46.6% (525 cases). ICU admission rates were also elevated for individuals aged ≥65 years at 5.7% (64 cases) and for those aged 0 years at 1.9% (2 cases). School-age children and adolescents (ages 7–18 years), who reported the highest number of cases, had a hospitalization rate of 9.9% (4,062 cases), with an ICU rate of 0.01% (3 cases), the lowest among all age groups. The prevalence of dyspnea, a severe symptom, was 0.8% (320 cases), notably lower than in other age groups. The average time from symptom onset to diagnosis was 7.5 days overall. This duration was relatively short for those aged <19 years at less than 9 days, whereas for adults aged ≥19 years, the average exceeded 10 days, indicating a tendency for delayed diagnosis of pertussis (Table 3).
Table 3. Age-specific clinical characteristics of confirmed and suspected pertussis cases, 2024.
| Category | Total (n=47,637) |
0 yr (n=108) |
1–6 yr (n=1,633) |
7–18 yr (n=41,076) |
19–64 yr (n=3,694) |
≥65 yr (n=1,126) |
|---|---|---|---|---|---|---|
| Main symptom | ||||||
| Cough | 47,525 (99.8) | 108 (100.0) | 1,625 (99.5) | 41,019 (99.9) | 3,678 (99.6) | 1,095 (97.2) |
| Paroxysmal cough | 7,336 (15.4) | 22 (20.4) | 209 (12.8) | 6,332 (15.4) | 615 (16.6) | 158 (14.0) |
| Whooping | 5,842 (12.3) | 8 (7.4) | 209 (12.8) | 4,912 (12.0) | 529 (14.3) | 184 (16.3) |
| Dypnea | 581 (1.2) | 6 (5.6) | 20 (1.2) | 320 (0.8) | 137 (3.7) | 98 (8.7) |
| Vomiting | 1,406 (3.0) | 10 (9.3) | 72 (4.4) | 1,214 (3.0) | 96 (2.6) | 14 (1.2) |
| Hospitalized status | ||||||
| Admitted | 5,500 (11.5) | 51 (47.2) | 378 (23.1) | 4,062 (9.9) | 484 (13.1) | 525 (46.6) |
| ICU admission | 82 (0.2) | 2 (1.9) | 0 (0.0) | 3 (0.01) | 13 (0.4) | 64 (5.7) |
| Symptom onset to diagnosisa) (mean±SD) (day) | 7.5±7.6 | 8.3±9.8 | 7.1±7.8 | 7.2±7.1 | 10.3±10.1 | 10.2±10.1 |
Unit: case (%). ICU=intensive care unit; SD=standard deviation. a)The duration from symptom onset to diagnosis was calculated, excluding 94 cases with missing or unclear information on the date of symptom onset (n=47,543).
The outbreak that commenced in Gyeongsangnam-do in early 2024 exhibited a pattern of nationwide dissemination, with the Seoul Metropolitan Area serving as a main epicenter. In 2024, reported cases were concentrated in the Seoul Metropolitan Area, with the highest incidence in Gyeonggi-do, followed by Seoul and Incheon. Nonetheless, epidemic cases were reported in all other regions. A comparison of cumulative incidence rates per 100,000 population revealed that Incheon, Jeju-do, and Gyeongsangnam-do exhibited the highest incidence rates relative to their respective populations (Table 4).
Table 4. Regional distribution of confirmed and suspected pertussis cases, 2024.
| Region | No. of cases | Proportion of total cases (%) | Cumulative incidence per 100,000 populationa) |
|---|---|---|---|
| Seoul | 6,017 | 12.5 | 64.5 |
| Busan | 2,820 | 5.9 | 86.3 |
| Daegu | 2,477 | 5.2 | 104.8 |
| Incheon | 4,351 | 9.1 | 144.0 |
| Gwangju | 879 | 1.8 | 62.4 |
| Daejeon | 1,240 | 2.6 | 86.2 |
| Ulsan | 640 | 1.3 | 58.3 |
| Sejong | 409 | 0.9 | 104.7 |
| Gyeonggi-do | 14,317 | 29.8 | 104.5 |
| Gangwon-do | 1,554 | 3.2 | 102.4 |
| Chungcheongbuk-do | 773 | 1.6 | 48.6 |
| Chungcheongnam-do | 1,896 | 3.9 | 88.7 |
| Jeollabuk-do | 1,328 | 2.8 | 76.4 |
| Jeollanam-do | 1,995 | 4.2 | 111.5 |
| Gyeongsangbuk-do | 2,231 | 4.6 | 88.1 |
| Gyeongsangnam-do | 4,157 | 8.7 | 128.8 |
| Jeju-do | 964 | 2.0 | 143.8 |
a)Based on the resident population statistics published by the Ministry of the Interior and Safety as of December 2024.
Among the 48,048 total reported cases in 2024, the latest vaccination status by age group was determined for 43,777 cases (91.1%) with verifiable vaccination histories. Individuals aged ≥12 years were classified as “unknown” due to the absence of recorded vaccination history in the Integrated Vaccination Management System. By age group, 0.5% (110 cases) were aged 7–12 years, 0.9% (179 cases) were aged 13–18 years, and 81.6% (3,982 cases) were aged ≥19 years. Among cases involving infants aged 0 years, who are recommended to receive a total of three doses of the primary vaccination series by 6 months of age, 24.1% (26 cases) completed the first dose, 14.8% (16 cases) completed the second dose, and 43.5% (47 cases) completed the third dose. Unvaccinated cases accounted for 17.6% (19 cases) of the total. Within this group, 9 cases (47.4%) were infants under 2 months of age who had not yet reached the vaccination age, while 10 cases (52.6%) were eligible for vaccination but had no recorded vaccination history. The age group of 1–6 years is advised to receive the fourth (for those aged 15–18 months) and fifth (for those aged 4–6 years) vaccinations. The latest vaccination status for this age group was confirmed as follows: 2.1% (34 cases) were unvaccinated, 46.3% (762 cases) completed the fourth vaccination, and 45.8% (754 cases) completed the fifth vaccination. For the age group of 7–12 years, the recommendation includes the fifth dose (for those aged 11–12 years) and the sixth dose (for those aged ≥13 years). The latest vaccination status for this group was as follows: 79.7% (17,127 cases) completed the fifth dose, 18.5% (3,985 cases) completed the sixth dose, and 0.2% (50 cases) were unvaccinated. Among individuals aged 13–18 years, the completion rate for the recommended sixth dose was 87.3% (17,393 cases), while for adults aged 19 and older, the completion rate for the sixth dose was 13.6% (665 cases).
3. 2024 Pertussis Outbreak Cases (Provisional Statistics)
Of the 2,770 total pertussis outbreak cases registered in 2024, an analysis was conducted on 2,118 cases (76.5% of all outbreak cases), excluding those with only one reported patient and those with incomplete reports. The total number of reported patients and suspected cases in this outbreak was 14,654, which represents 30.5% of all pertussis cases reported in 2024 (48,048 cases). However, given that this study’s sample size was limited to a proportion (76.5%) of all outbreak cases, the number of reported patients and suspected cases in the analyzed outbreak cases (14,654) was adjusted by the analysis ratio (0.765). This adjustment estimated that outbreak cases accounted for 39.9% of all reported cases.
Regionally, the Seoul Metropolitan Area accounted for the largest share, comprising 60.4% (1,279 cases) of the total group. The Gyeongnam region followed with 316 cases (14.9%), the Honam region (including Jeju Island) with 214 cases (10.1%), the Gyeongbuk region with 175 cases (8.3%), and the Chungcheong region with 134 cases (6.3%). By facility type, the outbreak was predominantly concentrated in schools, with elementary schools reporting the highest number of cases (961 cases, 45.4%), followed by middle schools (730 cases, 34.5%), high schools (367 cases, 17.3%), and other facilities (including education and childcare facilities, healthcare organizations) (60 cases, 2.8%). In terms of outbreak size, small-scale outbreaks involving 10 or fewer cases accounted for the majority, totaling 1,767 cases (83.4%). Outbreaks involving 11 to 50 cases numbered 332 (15.7%), while those exceeding 50 cases totaled 19 (0.9%). The average outbreak size per facility was seven cases (range: 2–136 cases). The average number of patients by facility type was six in elementary schools, 8 in middle schools, 8 in high schools, and four in other facilities (Supplementary Table 1; available online).
Discussion
The total number of reported pertussis cases in ROK for the year 2024 reached 48,048, representing a nearly 49-fold increase from the previous peak of 980 cases in 2018 and constituting the largest outbreak since the establishment of the infectious disease surveillance system. The epidemic, which commenced in the first half of 2024, exhibited a significant escalation in cases during the latter half, suggesting widespread transmission across the nation. The incidence during the initial 6 months of 2025 has remained elevated compared to prior periods; however, it is demonstrating a downward trend while maintaining a relatively stable pattern.
In contrast to earlier trends wherein pertussis outbreaks predominantly affected children under 6 years of age and adults, the outbreaks observed in 2024 and the first half of 2025 primarily impacted school-age children and adolescents (aged 7–18 years) (Figure 1). This shift underscores the necessity for a collaborative multi-agency response system to effectively manage outbreaks in schools and prevent community transmission. Additionally, during 2024, there were 108 reported cases involving infants under 1 year of age, including one unvaccinated infant fatality. An analysis of the vaccination history of pertussis cases reported in 2024 indicated that among high-risk cases under 1 year of age, 17.6% (19 cases) were unvaccinated. Of these, 47.4% (9 cases) were unable to receive the vaccine due to not having reached the recommended vaccination age, while the remaining 52.6% (10 cases) did not receive the vaccine despite being eligible. This finding highlights the critical need for vaccinating infants under 1 year of age and pregnant women to safeguard high-risk populations, suggesting the necessity for a strategic approach.
Figure 1. Trends in age-specific proportions of confirmed and suspected pertussis cases, from 2016 to the first half of 2025.
As the global pertussis outbreak continues to expand, various hypotheses have been proposed regarding the etiology of the domestic outbreak. The emergence of vaccine-evading variants, including declining immunity, the persistence of the aP vaccine, and pertactin deficiency, alongside the ptxP3 lineage, have been identified as significant contributors to recent outbreaks in the country. A considerable proportion of patients reported having completed their vaccination series, and some cases of reinfection have been confirmed.
Moreover, the concept of “immunity debt,” resulting from reduced opportunities for natural infection during the COVID-19 pandemic, has emerged as a critical factor in the escalation of domestic outbreaks. The stringent quarantine measures implemented during the pandemic temporarily diminished the incidence of infectious diseases; however, they also deprived the population of opportunities to bolster immunity through natural virus circulation. Consequently, following the relaxation of these measures, a rapid resurgence of cases occurred, particularly among populations with compromised immunity [10,11]. Notably, the majority of these cases were among school-age children and adolescents living in densely connected communities, a significant contributing factor to the magnitude of this outbreak.
Furthermore, the increased frequency of polymerase chain reaction (PCR) testing following the enhancement of diagnostic systems in the wake of the COVID-19 pandemic appears to have contributed to the rise in cases among school-age children and adolescents. Proactive responses and enhanced surveillance by educational institutions facilitated rapid diagnosis and reporting, even for relatively mild symptoms, resulting in a high reporting rate among this demographic. Conversely, adults often experienced milder symptoms, which might have led to delayed diagnosis or underreporting. In fact, adults exhibited a higher hospitalization rate relative to the number of cases, with the longest average time from symptom onset to diagnosis, indicating a tendency for pertussis to be diagnosed in more severe or hospitalized states. This discrepancy in surveillance sensitivity appears to have influenced the observed age-specific incidence gap.
The PCR test targeting the IS481 gene may have inflated the reported scale of the epidemic, as it can detect not only B. pertussis but also other closely related species within the Bordetella genus that present symptoms similar to pertussis [12]. A subsequent analysis of 234 specimens confirmed positive for B. pertussis, collected in June 2024, revealed the presence of Bordetella holmesii in approximately 25% of the cases (60). This finding suggests the potential for concurrent circulation of B. pertussis and its closely related species in domestic settings, highlighting the imperative need for enhanced pathogen surveillance systems [13]. In neighboring countries such as China, Japan, and several European nations, genetic mutations in B. pertussis and strains resistant to macrolide antimicrobials have been identified, raising concerns about treatment failures and the potential for epidemic spread [5,6,14,15]. Despite the limited domestic data on antimicrobial-resistant bacteria affecting pertussis treatment, instances of low treatment response or re-diagnosis have been documented, emphasizing the necessity for ongoing monitoring of resistance in the future.
In response to this situation, the KDCA implemented a multifaceted array of public health measures informed by surveillance and epidemiological data. Recommendations for tetanus-diphtheria-pertussis (Tdap) vaccination during pregnancy have been intensified to protect infants under 1 year of age, alongside initiatives to promote vaccination among unvaccinated school-age children and adolescents. Furthermore, in collaboration with relevant ministries, the scope of covered healthcare benefits for preventive antimicrobial treatment has been broadened to include high-risk groups, such as infants under 12 months of age, patients with moderate-to-severe asthma, patients with chronic lung disease, their cohabitants, and women in the third trimester of pregnancy, thereby alleviating their financial burden. To address the challenges posed by community outbreaks, a cooperative framework was established through the formation of a respiratory disease task force comprising local governments, the Ministry of Education, the Ministry of Health and Welfare, the Ministry of Food and Drug Safety, and subject matter experts. Additionally, a collaborative response strategy was enacted, facilitating the continuous exchange of information with educational institutions and healthcare providers. Following the potential for simultaneous outbreaks of closely related species, positive samples were collected and analyzed, leading to the identification of B. holmesii in certain cases. Consequently, the diagnostic criteria were reviewed through expert consultation to ensure the validity and relevance of the established standards. Furthermore, the Vaccination Expert Committee revised the Tdap vaccination implementation criteria to expand vaccination coverage in response to the epidemic’s spread among school-age children and adolescents, transitioning from “Tdap or tetanus-diphtheria (Td)” to “Tdap” as determined in deliberations held in December 2024.
Although this study conducted a descriptive statistical analysis utilizing surveillance data based on pertussis case reports and epidemiological investigation reports, limitations prevented a detailed quantitative analysis of detailed factors such as clinical course, route of infection, and treatment outcomes for individual cases due to the restricted scope of collected items. Specifically, while data on “hospitalization” and “ICU admission” were gathered, it remains unclear whether these instances were due to direct hospitalization for pertussis, necessitating caution in interpreting severity by age group. Moreover, the absence of data regarding pathogen characteristics and macrolide antimicrobial resistance within the survey data impeded the analysis of the impact of these factors on epidemic patterns or severity.
This study analyzed the domestic reporting status of pertussis, as well as the epidemiological characteristics of pertussis patients and outbreak cases from 2024 through the first half of 2025. The underlying causes of the epidemic situation were examined, and a summary of public health countermeasures was provided. Notably, with the sharp increase in reports primarily involving school-age children and adolescents, severe cases and fatalities have been confirmed among high-risk groups, such as infants under 1 year of age, underscoring the necessity for supplementary protective strategies. Pertussis is an infectious disease characterized by recurring, periodic epidemics. To prepare for potential large-scale outbreaks in the future, continuous surveillance and research are essential regarding vaccine efficacy, duration of immunity, antimicrobial resistance, and changes in infection patterns. Furthermore, the capacity to respond effectively to suppress outbreaks must be strengthened by enhancing vaccination strategies for pregnant women and infants who are not yet eligible for vaccination, thereby protecting high-risk groups and continuously reinforcing the multi-agency cooperation system for early diagnosis and community response.
Acknowledgments
The efforts of the Regional Centers for Disease Control and Prevention, local governments, and healthcare institutions in responding to the outbreak are gratefully acknowledged.
Supplementary Materials
Supplementary data are available online.
Declarations
Ethics Statement: Not applicable.
Funding Source: None.
Conflict of Interest: Young Joon Park is an editorial board member of the journal, but was not involved in the review process of this manuscript. Otherwise, there are no conflict of interest to declare.
Author Contributions: Conceptualization: HJK, YJP. Data curation: HJK, YEY, SYK, JL. Formal analysis: HJK. Investigation: HJK, YEY, SYK, JL. Methodology: HJK, DKK, YJP. Project administration: HJK, JHL, YJP, DKK, SRS, JSY. Resources: HJK, JHL, DKK, YEY, YJP, SYK, JL, JYS, WKL, SHA. Supervision: YJP. Validation: HJK. Visualization: HJK. Writing–original draft: HJK. Writing–review & editing: HJK, YJP, DKK, JHL, YKK, SRS, JSY, YEY, EBW, SBP, SYK, JL, JYS, WKL, SHA.
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