Background: South Korea introduced a national two-dose human papillomavirus (HPV) immunisation programme for 12-year-old girls in 2016. We assessed its early real-world effectiveness against anogenital warts. Methods: In this nationwide retrospective cohort study, we linked the Korea Disease Control and Prevention Agency immunisation registry to the National Health Insurance Service database. Females born in 2003–12 were classified by HPV vaccine type and number of doses received before a birth cohort-specific administrative vaccination deadline. Participants were followed until an incident diagnosis of anogenital warts, death, or Dec 31, 2024. Incidence rate ratios were estimated with Poisson regression, and vaccine effectiveness was calculated as one minus the incidence rate ratio. Findings: The analysis included 2,184,929 females, of whom 1,529,835 had received the quadrivalent or nonavalent vaccine and 655,094 were included in the comparison group. The adjusted effectiveness of at least one dose against anogenital warts was 58·4% (95% CI 53·1–63·2). Adjusted effectiveness was 56·2% (49·9–61·7) after two doses and 52·8% (37·1–64·6) after one dose. Effectiveness was 55·8% (49·1–61·7) in the 2003–04 birth cohorts, 64·0% (53·4–72·2) in the 2005–06 cohorts, and 64·9% (44·0–78·0) in the 2007–10 cohorts. Intepretation: HPV vaccination through South Korea’s national programme was associated with a substantially lower incidence of anogenital warts. Protection was observed after both one and two doses, although this observational study was not designed to establish equivalence between the schedules. Continued follow-up is needed to assess effectiveness against cervical precancer and cancer.

Objectives:The first National Influenza Annual Report was jointly released by the Korea Disease Control and Prevention Agency (KDCA) and the National Health Insurance Service (NHIS) to provide a comprehensive analysis of influenza activity and the burden of disease during the 2024-2025 influenza season. Methods:Influenza activity was analyzed using patient- and pathogen-based surveillance data, medical costs data, vaccination coverage, and vaccine effectiveness (VE) estimates. Data were obtained from the KDCA sentinel surveillance system, the National Immunization Program, and the NHIS national health information databases. VE was estimated using both a target trial emulation (TTE)-based retrospective cohort design to assess age-specific outcomes and an interrupted time series (ITS) method with dynamic cohort to evaluate time-varying protection. Results:During the 2024-2025 season, influenza-like illness peaked at 99.8 cases per 1,000 outpatients in the first week of 2025, the highest level recorded since 2016. The overall influenza virus detection rate was 15.2%, with a winter wave dominated by influenza A and a spring wave of influenza B. NHIS claims identified approximately 3.86 million influenza cases, indicating a decline from the previous season. Despite this decrease in case numbers, total medical costs continued to increase in the post-coronavirus disease 2019 period, reaching 629.5 billion KRW, with hospitalization accounting for 77.3% of the total costs. Vaccination coverage was 70.0% among children aged 6 months to 13 years and 81.6% among adults aged 65 years and older. The TTE analysis showed that VE against severe outcomes ranged from 63.7% to 74.6%, whereas VE against mortality ranged from 52.2% to 81.1%, depending on the age group. The ITS method demonstrated that protection against hospitalization (VE 41.8%) persisted for up to 2 months after vaccination, whereas protection against mortality (VE 38.1%) persisted for up to 6 months. Overall, influenza vaccination was estimated to have prevented 143,868 influenza cases, including outpatient and inpatient cases, as well as 3,506 deaths. Conclusions:The findings presented in this annual report provide scientific evidence for optimizing national influenza prevention and response strategies and advancing immunization policy.

Background: Understanding disparities in severe coronavirus disease 2019 (COVID-19) outcomes between people with disabilities (PwD) and people without disabilities (PwoD) is crucial, particularly when considering the heterogeneity within PwD and age differences. This study aimed to compare severe COVID-19 outcomes including deaths between PwD and PwoD with analyses stratified by age group and further examined by disability type. Methods: This retrospective, population-based cohort study used linked data from national COVID-19 cases and health insurance for individuals aged >= 19 years with COVID-19 from January 2020 to October 2022 in the Republic of Korea. Severe outcomes included severe cases and deaths, with logistic regression analysis of the risk disparities between PwD and PwoD based on age group and disability types. The subgroup analysis considered epidemic periods, accounting for the severe acute respiratory syndrome coronavirus 2 variant circulation. Results: The risk of severe COVID-19 outcomes and deaths among PwD varied by age and disability type. While severe outcomes were most prevalent in the older age groups for both PwD and PwoD, younger PwD faced a markedly higher risk-up to eightfold-compared to PwoD. The risk of disability status was greater than that of comorbidities in the 19-39 age group. Among disability types, individuals with internal organs-related and intellectual disabilities showed higher risk disparities with PwoD in severe outcomes than other types of disabilities. Throughout the pandemic, the disparity in death risk remained similar, with a slight increase in disparity during the omicron period for all severe outcomes in the age groups 19-39 and 40-64 years. Conclusion: Prioritizing younger PwD, along with older age groups and people with comorbidities, is crucial in addressing public health crises. Risk-based prioritization is important to reduce overall risk. This includes prioritizing people with nternal organs-related and intellectural disabilities, who face higher health risks among PwD during a pandemic when resources are limited and time is of the essence.

Objectives We analyzed the demographic and clinical characteristics of patients diagnosed with coronavirus disease 2019 (COVID-19), focusing specifically on severe/critical cases, and assessed the trends and rates of severity and fatality among these patients in the Republic of Korea. Methods Clinical data on patients with COVID-19 from January 20, 2020 to August 30, 2023 were collected from the Korea Disease Control and Prevention Agency’s database. We identified patients who progressed to severe/critical conditions and analyzed their demographic and clinical profiles. Severity and fatality rates were calculated and compared annually to track the disease progression over time. Results During the surveillance period, 34,572,554 COVID-19 cases were confirmed, among whom 38,112 (0.11%) progressed to severe/critical conditions. Most severe/critical cases occurred in individuals aged ≥60 years, with a notable increase in patients aged ≥80 years from 2022. The overall severity rate was 0.19%, with a fatality rate of 0.10%. However, the severity of cases gradually diminished during the study period. In 2022, the severity and fatality rates decreased to 0.14% and 0.09%, respectively. In 2023, while the severity rate remained stable at 0.15%, the fatality rate further decreased to 0.06%. Notably, throughout the study period, individuals aged ≥80 years had a significantly higher severity rate (2.44%), with a fatality rate of 1.75%. Conclusion These findings underscore the importance of prioritizing protection and management strategies for older adults and high-risk groups to mitigate the impact of COVID-19. Continued surveillance and analysis are essential to effectively control COVID-19 and minimize its burden on public health.

Objectives:During the initial outbreak of coronavirus disease 2019 (COVID-19), numerous predictive studies were conducted amid high uncertainty regarding the characteristics of the virus, and the study results were considered in the policymaking process. Methods:This study systematically analyzed research papers that predicted the spread of COVID-19 in the Republic of Korea. Focusing on 138 studies published between 2020 and October 15, 2024, it examined the data and methodologies employed and explored ways to enhance the utility of predictive outcomes in managing infectious disease outbreaks. Results:These methodologies included mathematical models, statistical models, and machine learning-based approaches to predict COVID-19 spread patterns. Beyond forecasting future outbreak trends, these predictive models were also instrumental in evaluating existing measures and proposing effective policies through scenario-based assumptions. Conclusions:This study's findings highlight the importance of multidisciplinary collaboration in developing predictive models to effectively prepare for and respond to infectious diseases. By doing so, it aims to minimize the public health impacts of infectious diseases.

Background: The persistent coronavirus disease 2019 (COVID-19) pandemic has had direct and indirect effects on mortality, making it essential to analyze excess mortality to fully understand the impact of the pandemic. In this study, we constructed a mathematical model using number of deaths from Statistics Korea and analyzed excess mortality between 2020 and 2022 according to age, sex, and dominant severe acute respiratory syndrome coronavirus 2 variant period. Methods: Number of all-cause deaths between 2010 and 2022 were obtained from the annual cause-of-death statistics provided by Statistics Korea. COVID-19 mortality data were acquired from the Korea Disease Control and Prevention Agency. A multivariate linear regression model with seasonal effect, stratified by sex and age, was used to estimate the number of deaths in the absence of COVID-19. The estimated excess mortality rate was calculated. Results: Excess mortality was not significant between January 2020 and October 2021. However, it started to increase monthly from November 2021 and reached its highest point during the omicron-dominant period. Specifically, in March and April 2022, during the omicron BA.1/BA.2-dominant period, the estimated median values for excess mortality were the highest at 17,634 and 11,379, respectively. Both COVID-19-related deaths and excess mortality increased with age. A notable increase in excess mortality was observed in individuals aged >= 65 years. In the context of excess mortality per 100,000 population based on the estimated median values in March 2022, the highest numbers were found among males and females aged >= 85 years at 1,048 and 910, respectively. Conclusion: This study revealed that the prolonged COVID-19 pandemic coupled with its high transmissibility not only increased COVID-19-related deaths but also had a significant impact on overall mortality rates, especially in the elderly. Therefore, it is crucial to concentrate healthcare resources and services on the elderly and ensure continued access to healthcare services during pandemics. Establishing an excess mortality monitoring system in the early stages of a pandemic is necessary to understand the impact of infectious diseases on mortality and effectively evaluate pandemic response policies.

This report analyzes the characteristics of coronavirus disease 2019 (COVID-19) cases collected through mandatory surveillance between January 20, 2020 and August 30, 2023, by age, sex, and region. During the mandatory surveillance period, 34,572,554 cases, 35,605 deaths, and 38,112 severe/critical cases were recorded. The number of COVID-19 cases gradually increased in 2020 and 2021; however, the cases surged, with 82.2% of the pandemic's total cases reported in 2022, after the omicron variant became the dominant strain in January 2022. In March 2022, 9,959,368 cases were reported, accounting for the highest proportion (28.8%) of total cases. Individuals in their 40s (15.1%) and 30s (14.7%) represented the highest proportion of cases during the study period. Annually, the highest proportion of cases in 2020, 2021, 2022, and 2023 were observed among individuals in their 50s, 20s, 40s, and 30s, respectively. Regionally, metropolitan region accounted for 52.1% of the total cases. In non-metropolitan regions, most cases in 2020 were reported in Daegu and Gyeongbuk and increased in Busan, Ulsan, and Gyeongnam thereafter. This report complies with and conveys information on the characteristics of COVID-19 cases reported during the mandatory surveillance period. This report may serve as a reference for future respiratory infectious disease crises.

Background As the population acquires immunity through vaccination and natural infection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), understanding the intrinsic severity of coronavirus disease (COVID-19) is becoming challenging. We aimed to evaluate the intrinsic severity regarding circulating variants of SARS-CoV-2 and to compare this between vaccinated and unvaccinated individuals. Methods With unvaccinated and initially infected confirmed cases of COVID-19, we estimated the case severity rate (CSR); case fatality rate (CFR); and mortality rate (MR), including severe/critical cases and deaths, stratified by age and compared by vaccination status according to the period regarding the variants of COVID-19 and vaccination. The overall rate was directly standardized with age. Results The age-standardized CSRs (aCSRs) of the unvaccinated group were 2.12%, 5.51%, and 0.94% in the pre-delta, delta, and omicron period, respectively, and the age-standardized CFRs (aCFRs) were 0.60%, 2.49%, and 0.63% in each period, respectively. The complete vaccination group had lower severity than the unvaccinated group over the entire period showing under 1% for the aCSR and 0.5% for the aCFR. The age-standardized MR of the unvaccinated group was 448 per million people per month people in the omicron period, which was 11 times higher than that of the vaccinated group. In terms of age groups, the CSR and CFR sharply increased with age from the 60 s and showed lower risk reduction in the 80 s when the period changed to the omicron period. Conclusions The intrinsic severity of COVID-19 was the highest in the delta period, with over 5% for the aCSR, whereas the completely vaccinated group maintained below 1%. This implies that when the population is vaccinated, the impact of COVID-19 will be limited, even if a new mutation appears. Moreover, considering the decreasing intrinsic severity, the response to COVID-19 should prioritize older individuals at a higher risk of severe disease.

The application of geospatial data often allows the tracing of people who are involved in activities of an illegal nature. In June 2021, we estimated the true magnitude of the spread of COVID-19 within the networks of escort-karaoke bars in Seoul, Republic of Korea, using geographic information system (GIS)-based contact tracing that was applied to our epidemiological investigation. Our joint rapid response team, composed of epidemic investigation officers and police personnel, identified 19 paper-traced cases and 158 GIS-traced cases from 5,692 confirmed cases in Seoul during the study period (June to July 2021). Our findings suggest that collaboration with law enforcement agencies and the use of overlaid satellite imagery in outbreak investigations enhances high vigilance and reduces the risk of potential breaches of human rights in the process.

BACKGROUND:We aimed to analyze the risk factors for sudden death after diagnosis of coronavirus disease 2019 (COVID-19) in South Korea and to provide evidence for informing prevention and control interventions for patients at risk of sudden death.METHODS:We included 30,302 COVID-19 related deaths registered in the patient management information system (Central Disease Control Headquarters) between January 1, 2021, and December 15, 2022. We collected their epidemiological data recorded by the reporting city, province, or country. We performed multivariate logistic regression analysis to identify risk factors for sudden death after diagnosis of COVID-19.RESULTS:Among the 30,302 deaths, there were 7,258 (24.0%) and 23,044 (76.0%) sudden and non-sudden deaths, respectively. Sudden death means a person who died within 2 days of diagnosis and who did not receive inpatient treatment. Underlying condition, vaccination status, and place of death were significantly associated with the survival period in all age groups. Moreover, region, sex, and prescription were significantly associated with the survival period only in certain age groups. However, reinfection was not significantly associated with the survival period in any age group.CONCLUSION:To our knowledge, this is the first study on the risk factors for sudden death after a diagnosis of COVID-19, which included age, underlying condition, vaccination status, and place of death. Additionally, individuals aged < 60 years without an underlying condition were at high risk for sudden death. However, this group has relatively low interest in health, as can be seen from the high non-vaccination rate (16.1% of the general population vs. 61.6% of the corresponding group). Therefore, there is a possibility for the presence of an uncontrolled underlying disease in this population. In addition, many sudden deaths occurred due to delayed hospital visits to continue economic activities even after the onset of COVID-19 symptoms (7 days overall vs. 10 days average for the group). In conclusion, 'continued interest in health' is a key factor in avoiding sudden death in the economically active group (under 60 years of age).

질병관리청 중앙방역대책본부 역학조사분석단 정보분석팀, 2 질병관리청 위기대응분석관 위기대응연구담당관 초 록 코로나바이러스감염증-19(코로나19)는 SARS-CoV-2 바이러스에 의해 발생하는 감염병으로, 호흡기 증상이 주요 증상이며, 일부 고령자와 기저질환자의 경우에는 입원치료를 필요로 한다.변이바이러스 특성에 따라 전파력, 백신 효과, 중증도 등이 다르게 나타나 기 때문에 세계보건기구(World Health Organization)에서는 변이바이러스에 대해 추적 모니터링을 수행하고 있으며, 국내에서도 변 이바이러스 분석 및 정보를 수집하고 있다.본 보고서는 변이바이러스 우세종화 시기에 따른 국내 코로나19 중증도 추이를 비교, 분석 하기 위해서 2020년 1월 20일부터 2023년 7월 31일까지 코로나19 확진자의 중증도를 전 기간과 코로나19 변이바이러스 우세종화 시 기별로 구분하여 분석하였다.코로나19가 발생한 이후 2023년 7월 31일까지 총 34,082,179명의 확진자가 발생하였고, 그 중 37,760 명(0.11%)의 위중증 환자와 35,644명(0.11%)의사망자가 발생하였다.위중증 환자와 사망자는 오미크론 BA.1, BA.2 우세종화 시기 (2022.1.16.-2022.7.9.)에 가장 많이 발생하여 위중증 10,460명(27.7%),사망자 18,679명(52.4%)이었다.중증화율 및 치명률의 경 우, 델타변이 우세 이전 시기(2020.1.20.-2021.7.24.)에 각각 2.98%, 1.15%로 전 기간 중 가장 높았으며, 오미크론 XBB 우세종화 시기 (2023.4.16.-2023.7.31.)에 각각 0.12%, 0.04%로 가장 낮았다.코로나19 발생 이후 새로운 변이바이러스는 지속적으로 출현하 고 있으나 오미크론 XBB 우세종화 시기 치명률은 0.04%로 인플루엔자 수준의 위험도로 낮아졌다.다만, 연령대별 치명률은 0-49세 <0.01%, 50-59세 0.01%, 60-69세 0.03%인 반면, 80세 이상 연령대의 치명률은 0.56%로 다른 연령대에 비해 여전히 높아 고위험군 우선순위의 방역 정책은 지속되어야 하겠다.

This report seeks to compare and analyze the severity trends of coronavirus disease 2019 (COVID-19) in Republic of Korea during periods of dominant variant virus prevalence. The analysis covers the period from January 20, 2020, to July 31, 2023, categorizing the severity of COVID-19 cases both throughout the entire period and during periods of dominant variant virus prevalence. Up until July 31, 2023, a total of 34,082,179 confirmed cases of COVID-19 have been recorded, resulting in 37,760 cases (0.11%) of severe illness and 35,644 deaths (0.11%). During the dominant prevalence of the Omicron BA.1 and BA.2 variants (from January 16, 2022 to July 9, 2022), severe cases and deaths were most widespread, accounting for 10,460 cases (27.7%) of severe illness and 18,679 deaths (52.4%). Concerning case severity rate and case fatality rate, the period before the dominant prevalence of the Delta variant (from January 20, 2020 to July 24, 2021) had the highest rates at 2.98% and 1.15%, respectively. In contrast, during the dominant prevalence of the Omicron XBB variant (from April 16, 2023 to July 31, 2023), these rates were at their lowest, reaching 0.12% for severity and 0.04% for fatality. Despite the continuous emergence of new variant viruses after the onset of COVID-19, the case severity rate during the dominant prevalence of the Omicron XBB variant has decreased to 0.04%, comparable to the risk level seen with influenza. However, the case fatality rate by age group is <0.01% for 0-49 years old, 0.01% for 50-59 years old, and 0.03% for 60-69 years old, while the case fatality rate for 80+ years old is 0.56%, which is still higher than other age groups, so the prevention policy of prioritizing high-risk groups should be continued.

Objectives This study aimed to classify coronavirus disease 2019 (COVID-19)-related deaths according to whether COVID-19 was listed as the cause of death, and to investigate the differences in demographic characteristics and risk factors for COVID-19 death classifications. Methods A total of 5,625 deaths in South Korea among patients with confirmed COVID-19 from January 20, 2020 to December 31, 2021 were selected. Excluding false reports and unnatural deaths, 5,597 deaths were analyzed. Based on death report data, deaths were classified according to whether the cause of death was listed as COVID-19 (CD) or not (NCD). The epidemiological characteristics and causes of deaths were investigated using descriptive, univariate, and multivariate statistical analyses. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated to analyze the risk factors. Results The case fatality ratio was 0.89% and increased with age. Additionally, 96.4% of the subjects had an underlying disease, and 53.4% died in winter. The proportion of NCDs was 9.3%, of whom 19.1% died at home and 39.0% were confirmed to have COVID-19 after death. Malignant neoplasms (102/416 vs. 637/4,442; OR, 1.71; 95% CI, 1.36−2.16; p<0.001) were significantly associated with NCD. Conclusion This is the first study to analyze risk factors by cause of death using COVID-19 death report data in South Korea. These results are expected to be used as evidence for establishing a death monitoring system that can collect timely information in a new infectious disease pandemic.

As of September 3, 2022, 5,388,338 coronavirus disease 2019 (COVID-19) cases and 46 deaths (3 in 2021 and 43 in 2022) were reported in children ≤ 18 years in Korea. Cumulative confirmed cases accounted for 67.3% of the population aged ≤ 18 years and case fatality rate was 0.85/100,000. Among 46 fatal cases, 58.7% were male and median age was 7 years. Underlying diseases were present in 47.8%; neurologic diseases (63.6%) and malignancy (13.6%) most common. Only four had history of COVID-19 immunization. COVID-19 associated deaths occurred at median 2 days from diagnosis (range: -1 to 21). Among COVID-19 deaths, 41.3% occurred before admission; 2 before hospital arrival and 17 in the emergency department. Among children whose cause was documented, myocarditis, respiratory and multiorgan failure were most common. COVID-19 associated death was seen early after diagnosis in children and public health policies to provide access to medical care for children with COVID-19 are essential during the pandemic.

Boyeong Ryu, Eunjeong Shin, Na-Young Kim, Dong Hwi Kim, HyunJu Lee, Ahra Kim, Shin Young Park, Seonhee Ahn, Jinhwa Jang, Seong-Sun Kim, Donghyok Kwon*. Public Health Weekly Report 2022;15:2873-95. https://doi.org/10.56786/PHWR.2022.15.47.2873

Background: As of February 21, 2021, 86,992 cases of coronavirus disease 2019 (COVID-19) were confirmed in the Republic of Korea, with 1,557 deaths and 85,435 cases discharged from isolation. This study investigated the infectivity of individuals with COVID-19 who were retested and found to be severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) RNA-positive after recovering from their primary illness. Methods: We investigated 295 individuals with recurrent SARS-CoV-2 positive results, and 836 of their close contacts. We attempted virus isolation in 108 individuals with recurrent SARS-CoV-2 positivity using cell culture and confirmed the presence of neutralizing antibodies by means of serological tests. Findings: The average age was 45·2 years (range, 1–95 years) and 64% were female. At the time of retesting, 55·6% were asymptomatic, and symptoms included cough (18·0%), expectoration (11·2%), sore throat (10·8%), and fever (9·2%). The reasons for retesting were screening (46%), persistent symptoms (37·6%), and new contact with a confirmed COVID-19 case (9·5%). Virus isolation was attempted in 108 individuals with recurrent SARS-CoV-2 positivity, and all tested negative. Three new cases were identified among household contacts based on SARS-CoV-2 polymerase chain reaction testing. Two of the three new cases had had contact with the index patient during their primary illness, and all three had antibody evidence of past infection. Interpretation: There was no laboratory evidence of viral shedding and no epidemiological evidence of transmission among individuals with recurrent positivity. Funding Statement: This study was funded by the Korea Disease Control and Prevention Agency (No. 4800-4837-301). Declaration of Interests: The authors declare no conflicts of interest related to the study. Ethics Approval Statement: The study was approved by the KDCA Institutional Review Board (2020-03-01-P-A). The board waived the requirement for written informed consent.

Vaccination is considered to be the most effective measure for preventing the spread of coronavirus disease 2019 (COVID-19). Many countries, including of Korea, are focusing on achieving herd immunity with the goal of reaching a vaccination rate of 70-80%. However, achieving herd immunity does not mean eradicating COVID-19, and the following challenges can occur in the process of achieving herd immunity. First, as the vaccination rate is likely to slow down over time, it is necessary to promote the benefits of vaccination through risk communication strategies and provide incentives for those who have been vaccinated. Second, a booster dose may be required depending on future studies on vaccine-induced immunity. Third, since variants capable of evading immunity and with higher transmissibility can emerge, rapid contract tracing and regular community genomic surveillance could help mitigate the impact of new variants. When the impact of COVID-19 is controlled to the level of seasonal influenza, the current public health measures that have been strictly imposed on society since the beginning of the pandemic will no longer be needed. The overall response strategy to COVID-19 will need to change accordingly, based on evaluations of the level of population immunity. These changes will include more efficient and targeted contact tracing and eased quarantine measures for vaccinated close contacts and travelers. Mask wearing and a minimum of social distancing will still be required in the journey towards the end of the pandemic. The COVID-19 pandemic will end, but the virus will not disappear.