Abstract
Background
Respiratory syncytial virus (RSV) is a leading cause of lower respiratory tract infections in children. This study investigates the clinical characteristics, factors descriptively associated with severity, and shifts in age distribution of RSV infection in Korean children over an 11-year period.
Materials and Methods
Using electronic medical records from 21 referral hospitals, we conducted a retrospective observational study of children aged 0-4 years with RSV infection between 2012 and 2023. Data were converted to the Observational Medical Outcomes Partnership-Common Data Model. We compared clinical characteristics between those who received oxygen therapy or mechanical ventilation and those who did not.
Results
Of 9,625 children who tested positive for RSV, 79.3% were under two years of age and 99.2% were born at term. Among the 1,828 children who received oxygen therapy, 70.2% were aged 0–11 months and 98.8% were full-term, mirroring the overall cohort composition. Among the 104 children who received mechanical ventilation, 79.8% were aged 0–11 months. Within-group comparisons showed that age 0–11 months, male sex, preterm birth, developmental delay, perinatal lung disease, and cardiovascular disease were more frequently observed among children receiving oxygen therapy or mechanical ventilation than among those who did not.
Conclusion
RSV infection in our cohort predominantly affected young infants, with a post-pandemic shift toward older age groups. The high proportion of full-term infants without underlying conditions among severe cases reflected cohort composition rather than enriched risk. These hypothesis-generating findings suggest that broader prevention strategies covering all infants, alongside high-risk groups, warrant population-level evaluation.
Keywords: Respiratory syncytial virus, Infants, Children, Epidemiology, Korea
Graphical Abstract
Introduction
Respiratory Syncytial Virus (RSV) poses a significant global health burden, causing acute lower respiratory infections, contributing to millions of cases, hospitalizations, and deaths annually worldwide [1]. While RSV affects children of all ages, infants and young children with underlying health conditions are at the highest risk of severe illness and complications [2]. Recent estimates suggest that in 2019, there were 33 million episodes of RSV-associated ALRI in children under five years of age, resulting in approximately 3.1 million hospitalizations and over 100,000 deaths [3].
While the global burden of RSV is well-recognized, Korea-specific data spanning a long period and multiple referral hospitals remain limited. Most prior Korean reports are single-center or short-term [4]. Given the country’s tertiary-hospital structure and the recent change in RSV prevention policy, a multicenter, long-term description of pediatric RSV can help to inform local strategy.
In this study, we aimed to provide a comprehensive analysis of RSV infection in Korean children over an 11-year period. By using a large dataset from multiple referral hospitals and utilizing standardized electronic medical records, we sought to investigate the clinical characteristics, factors associated with disease severity, and temporal trends associated with RSV infection in this population.
Materials and Methods
1. Study design and data source
We conducted a retrospective observational study of 21 referral hospitals databases converted into the Observational Medical Outcomes Partnership-Common Data Model (OMOP-CDM) using the FEEDER-NET platform, which is a coordinating platform that enables data user and supplier connections and multi-institution analyses, with the anonymity of patients’ personal information, as applied in previous studies [5]. The included institutions are listed in Supplementary Table 1.
2. Ethics statement
The study protocol was reviewed and approved by the Institutional Review Board (IRB) of Korea University Anam Hospital (Approval No. 2022AN0114). This study was conducted in accordance with the Declaration of Helsinki. The requirement for obtaining informed consent was waived by the IRB because this study utilized a retrospective design involving data extracted from the OMOP-CDM database. All patient data were de-identified and anonymized prior to analysis to ensure the confidentiality of personal information, and the study involved no more than minimal risk to participants.
3. Variables of interest
We conducted a comprehensive literature review to identify potential factors reported in the literature to be associated with RSV-related severe outcomes including oxygen therapy or mechanical ventilation. Our analysis incorporated specific clinical data extracted from the CDM database, including demographic characteristics, preterm birth, developmental delays, pre-existing medical conditions, and palivizumab prophylaxis. Variables such as the length of observation, socioeconomic factors, presence of siblings, and maternal age, birth weight, gestational age, which were either unavailable in the electronic medical record or not translatable into the CDM, were excluded from our analysis.
Underlying diseases were categorized according to diagnosis codes into asthma, chromosomal anomalies, congenital malformations, malignancy, gastrointestinal disorders, cardiovascular diseases, and perinatal lung diseases. Oxygen therapy was identified using OMOP-CDM procedure concepts for any supplemental oxygen administration, including delivery via nasal cannula, simple mask, or high-flow nasal cannula. Mechanical ventilation was defined as invasive ventilation following endotracheal intubation; non-invasive modes such as CPAP and BiPAP were not included.
4. Study population
We conducted an analysis using the OMOP-CDM database, which encompassed data between August 2012 to December 2023. The eligibility criteria for children tested for RSV were defined based on the following parameters: (1) age range of 0 to 4 years, (2) visited hospital (inpatient, outpatient) for respiratory symptoms, and (3) confirmation of RSV testing through multiplex polymerase chain reaction (PCR). Subsequently, the RSV-positive group was categorized as follows: (1) children treated with or without oxygen therapy, and (2) children requiring or not requiring mechanical ventilation.
Although eligibility included both inpatient and outpatient index visits at which RSV PCR was performed, oxygen therapy and mechanical ventilation are coded as inpatient procedures within the OMOP-CDM at the participating sites. Severity outcomes therefore reflect hospitalized children.
5. Statistical analysis
Analyses were executed as standardized characterization queries within the FEEDER-NET federated environment; only aggregated counts were returned from each site, which precluded pooled patient-level multivariable modeling. Categorical variables were compared using the Chi-square or Fisher’s exact test based on the results from the ATLAS version 2.7.6. Continuous variables were expressed as means with standard deviations. Statistical significance was set at P<0.001. Statistical analyses were performed using R (version 4.4.0, R Foundation for Statistical Computing, Vienna, Austria).
Results
During the observed period, a total of 9,625 patients with respiratory symptoms tested positive for RSV. Among RSV-positive patients, 5,317 (55.2%) were male, and the 0–11 month (49.6%) and 12–23 month (29.8%) age groups accounted for 7,637 (79.3%) of the cohort. A total of 2,237 patients (23.2%) had at least one underlying medical condition, most frequently asthma (9.1%), gastrointestinal disorders (8.2%), and cardiovascular diseases (3.1%). Notably, only 2 patients (0.0%) in the entire cohort had a documented history of palivizumab prophylaxis. Regarding gestational age at birth, 75 (0.8%) were preterm births and 9,550 (99.2%) were full-term births. Mechanical ventilation and oxygen therapy were administered to 104 (1.1%) and 1,828 (19.0%) of the total patient population, respectively (Table 1).
Table 1. Overview of demographic and clinical characteristics of children tested positive for RSV, 2012-2023.
| Characteristic | Total (n=9,625) | |
|---|---|---|
| Sex, n (%) | ||
| Male | 5,317 (55.2) | |
| Female | 4,308 (44.8) | |
| Age group, n (%) | ||
| 0–11 mo | 4,770 (49.6) | |
| 12–23 mo | 2,867 (29.8) | |
| 24–35 mo | 1,350 (14.0) | |
| 3 yr | 468 (4.9) | |
| 4 yr | 170 (1.8) | |
| Year of test for diagnosis, n (%) | ||
| 2012 | 543 (5.6) | |
| 2013 | 568 (5.9) | |
| 2014 | 930 (9.7) | |
| 2015 | 1,135 (11.8) | |
| 2016 | 1,812 (18.8) | |
| 2017 | 1,440 (15.0) | |
| 2018 | 1,432 (14.9) | |
| 2019 | 1,011 (10.5) | |
| 2020 | 212 (2.2) | |
| 2021 | 43 (0.4) | |
| 2022 | 334 (3.5) | |
| 2023 | 165 (1.7) | |
| Gestational status, n (%) | ||
| Term infants | 9,550 (99.2) | |
| Preterm infants | 75 (0.8) | |
| Developmental delay, n (%) | 299 (3.1) | |
| Palivizumab prophylaxis, n (%) | 2 | |
| Underlying disease, n (%) | 2,237 (23.2) | |
| Asthma | 876 (9.1) | |
| Chromosomal anomalies | 10 (0.1) | |
| Congenital malformations | 252 (2.6) | |
| Malignancy | 0 | |
| Gastrointestinal disorder | 789 (8.2) | |
| Cardiovascular disease | 297 (3.1) | |
| Perinatal lung disease | 13 (0.1) | |
| No underlying disease, n (%) | 7,388 (76.8) | |
| Treatment, n (%) | ||
| Mechanical ventilation | 104 (1.1) | |
| Oxygen therapy | 1,828 (19.0) | |
RSV, respiratory syncytial virus; mo, month; yr, year.
Because >99% of the full cohort were full-term infants, the high proportion of full-term infants among children receiving oxygen therapy (1,806/1,828, 98.8%) or mechanical ventilation (101/104, 97.1%) reflects the demographic structure of the cohort rather than greater within-group risk. The same caveat applies to the high proportion without underlying disease (1,484/1,828, 81.2% for oxygen; 69/104, 66.3% for mechanical ventilation). Within-subgroup comparisons of severity by age, gestational status, and underlying disease are presented in Table 2. Factors descriptively associated with oxygen therapy and mechanical ventilation among RSV-positive children included male sex, preterm birth, and developmental delays.
Table 2. Characteristics and clinical outcomes of RSV positive patients from 2012 to 2023.
| Characteristic | No oxygen therapy (n=7,797) | Oxygen therapy (n=1,828) | P-value | No mechanical ventilation (n=9,521) | Mechanical ventilation (n=104) | P-value | |
|---|---|---|---|---|---|---|---|
| Sex, n (%) | 0.007 | 0.046 | |||||
| Male | 4,255 (54.6) | 1,062 (58.1) | 5,249 (55.1) | 68 (65.4) | |||
| Female | 3,542 (45.4) | 766 (41.9) | 4,272 (44.9) | 36 (34.6) | |||
| Age group, n (%) | <0.001 | <0.001 | |||||
| 0–11 mo | 3,486 (44.7) | 1,284 (70.2) | 4,687 (49.2) | 83 (79.8) | |||
| 12–23 mo | 2,443 (31.3) | 424 (23.2) | 2,852 (30.0) | 15 (14.4) | |||
| 24–35 mo | 1,271 (16.3) | 79 (4.3) | 1,345 (14.1) | 5 (4.8) | |||
| 3 yr | 432 (5.5) | 36 (2.0) | 467 (4.9) | 1 (1.0) | |||
| 4 yr | 165 (2.1) | 5 (0.3) | 170 (1.8) | 0 | |||
| Year of test for diagnosis, n (%) | <0.001 | 0.165 | |||||
| 2012 | 423 (5.4) | 120 (6.6) | 530 (5.6) | 13 (12.5) | |||
| 2013 | 478 (6.1) | 90 (4.9) | 562 (5.9) | 6 (5.8) | |||
| 2014 | 787 (10.1) | 143 (7.8) | 916 (9.6) | 14 (13.5) | |||
| 2015 | 954 (12.2) | 181 (9.9) | 1,123 (11.8) | 12 (11.5) | |||
| 2016 | 1,484 (19.0) | 328 (17.9) | 1,795 (18.9) | 17 (16.3) | |||
| 2017 | 1,142 (14.6) | 298 (16.3) | 1,423 (14.9) | 17 (16.3) | |||
| 2018 | 1,146 (14.7) | 286 (15.6) | 1,423 (14.9) | 9 (8.7) | |||
| 2019 | 806 (10.3) | 205 (11.2) | 1,001 (10.5) | 10 (9.6) | |||
| 2020 | 160 (2.1) | 52 (2.8) | 209 (2.2) | 3 (2.9) | |||
| 2021 | 33 (0.4) | 10 (0.5) | 43 (0.5) | 0 | |||
| 2022 | 262 (3.4) | 72 (3.9) | 332 (3.5) | 2 (1.9) | |||
| 2023 | 122 (1.6) | 43 (2.4) | 164 (1.7) | 1 (1.0) | |||
| Gestational status, n (%) | 0.032 | 0.047 | |||||
| Term infants | 7,744 (99.3) | 1,806 (98.8) | 9,449 (99.2) | 101 (97.1) | |||
| Preterm infants | 53 (0.7) | 22 (1.2) | 72 (0.8) | 3 (2.9) | |||
| Developmental delay, n (%) | 221 (2.8) | 78 (4.3) | 0.002 | 290 (3.0) | 9 (8.7) | 0.005 | |
| Palivizumab prophylaxis, n (%) | 0 | 2 (0.1) | 0.036 | 2 (0.0) | 0 | >0.999 | |
| No underlying disease, n (%) | 5,904 (75.7) | 1,484 (81.2) | <0.001 | 7,319 (76.9) | 69 (66.4) | 0.016 | |
| Underlying disease, n (%) | 1,893 (24.3) | 344 (18.8) | 2,202 (23.1) | 35 (33.6) | |||
| Asthma | 813 (10.4) | 63 (3.4) | <0.001 | 871 (9.1) | 5 (4.8) | 0.174 | |
| Chromosomal anomalies | 6 (0.1) | 4 (0.2) | 0.104 | 9 (0.1) | 1 (1.0) | 0.103 | |
| Congenital malformations | 186 (2.4) | 66 (3.6) | 0.004 | 246 (2.6) | 6 (5.8) | 0.055 | |
| Malignancy | 0 | 0 | - | 0 | 0 | - | |
| Gastrointestinal disorder | 671 (8.6) | 118 (6.5) | 0.003 | 782 (8.2) | 7 (6.7) | 0.713 | |
| Cardiovascular disease | 211 (2.7) | 86 (4.7) | <0.001 | 283 (3.0) | 14 (13.5) | <0.001 | |
| Perinatal lung disease | 6 (0.1) | 7 (0.4) | 0.005 | 11 (0.1) | 2 (1.9) | 0.008 | |
P-values were calculated using the chi-square test or Fisher's exact test, as appropriate.
P<0.001 was considered statistically significant.
RSV, respiratory syncytial virus; mo, month; yr, year.
Among underlying diseases, cardiovascular disease and perinatal lung disease were observed more frequently among children who received supplemental oxygen or mechanical ventilation (Table 2). RSV-positive patients who received either oxygen therapy or mechanical ventilation exhibited the highest absolute numbers of preterm birth (12 and 2 cases, respectively) and developmental delay (41 and 7 cases, respectively) in the 0–11 month age group. Additionally, this age group had the highest proportion of patients with underlying diseases such as gastrointestinal disorder (73 and 6 cases, respectively) and cardiovascular disease (54 and 13 cases, respectively) (Table 3, Table 4). Among children aged ≥24 months, only 1 of 120 (0.8%) who received oxygen therapy and 0 of 6 who received mechanical ventilation were preterm. The numbers are too small to draw conclusions about the residual contribution of prematurity beyond infancy.
Table 3. Characteristics and clinical outcomes of RSV positive patients who were treated with oxygen therapy from 2012 to 2023 distributed by age.
| Characteristic | 0–11 months (n=1,284) | 12–23 months (n=424) | 24–35 months (n=79) | 36–47 months (n=36) | 48–59 months (n=5) | P-value | |
|---|---|---|---|---|---|---|---|
| Preterm birth, n (%) | 12 (0.9) | 9 (2.1) | 1 (1.3) | 0 | 0 | — | |
| Developmental delay, n (%) | 41 (3.2) | 30 (7.1) | 6 (7.6) | 1 (2.8) | 0 | — | |
| Palivizumab prophylaxis, n (%) | 1 (0.1) | 1 (0.2) | 0 | 0 | 0 | 0.075 | |
| Type of underlying disease, n (%) | |||||||
| Asthma | 22 (1.7) | 19 (4.5) | 14 (17.7) | 7 (19.4) | 1 (20.0) | — | |
| Chromosomal anomaly | 3 (0.2) | 1 (0.2) | 0 | 0 | 0 | 0.083 | |
| Congenital malformation | 33 (2.6) | 27 (6.4) | 5 (6.3) | 1 (2.8) | 0 | — | |
| Malignancy | 0 | 0 | 0 | 0 | 0 | — | |
| Gastrointestinal disorder | 73 (5.7) | 32 (7.5) | 10 (12.7) | 3 (8.3) | 0 | — | |
| Cardiovascular disease | 54 (4.2) | 27 (6.4) | 4 (5.1) | 1 (2.8) | 0 | — | |
| Perinatal lung disease | 2 (0.2) | 5 (1.2) | 0 | 0 | 0 | 0.003 | |
P-values were calculated using the chi-square test or Fisher’s exact test, as appropriate.
The dash indicates that a statistical comparison was not performed or could not be reliably estimated because of sparse data.
Patients may have had more than one underlying disease.
Table 4. Characteristics and clinical outcomes of RSV positive patients who were treated with mechanical ventilation from 2012 to 2023 distributed by age.
| Characteristic | 0–11 months (n=83) | 12–23 months (n=15) | 24–35 months (n=5) | 36–47 months (n=1) | 48–59 months (n=0) | P-value | |
|---|---|---|---|---|---|---|---|
| Preterm birth, n (%) | 2 (2.4) | 1 (6.7) | 0 | 0 | — | 0.054 | |
| Developmental delay, n (%) | 7 (8.4) | 2 (13.3) | 0 | 0 | — | — | |
| Palivizumab prophylaxis, n (%) | 0 | 0 | 0 | 0 | — | >0.999 | |
| Underlying diseases, n (%) | |||||||
| Asthma | 3 (3.6) | 1 (6.7) | 0 | 1 (100) | — | — | |
| Chromosomal anomaly | 1 (1.2) | 0 | 0 | 0 | — | 0.037 | |
| Congenital malformation | 4 (4.8) | 2 (13.3) | 0 | 0 | — | — | |
| Malignancy | 0 | 0 | 0 | 0 | — | — | |
| Gastrointestinal disorder | 6 (7.2) | 0 | 1 (20.0) | 0 | — | — | |
| Cardiovascular disease | 13 (15.7) | 1 (6.7) | 0 | 0 | — | — | |
| Perinatal lung disease | 1 (1.2) | 1 (6.7) | 0 | 0 | — | 0.004 | |
P-values were calculated using the Chi-square test or Fisher’s exact test, as appropriate.
The dash indicates that a statistical comparison was not performed.
Patients may have had more than one underlying disease.
During the study period from 2012 to 2023, the 0–11 month group accounted for a major proportion (44.7–63.7%) of RSV-positive patients each year between 2012 and 2019. Thereafter, the predominant age group among RSV-positive patients shifted from 0–11 months to 1–3 years between 2020 and 2023 (Fig. 1). Prior to the pandemic (2012–2019), the 0–11 month age group (represented by the blue bars) consistently formed the highest peak of infection. However, following the marked suppression of RSV cases in 2020 and 2021, the subsequent rebound in 2022 and 2023 showed a notable upward shift in the affected age groups. In 2022, the 12–23 month group (orange bars) overtook the infant group as the primary peak, and in 2023, both the 12–23 month and 24–35 month groups (green bars) represented a substantially larger proportion of cases compared to the pre-pandemic baseline.
Figure 1. The number of RSV positive patients by age from 2012 to 2023.
RSV, respiratory syncytial virus.
Discussion
We observed a shift in the age distribution of RSV infections following the onset of the coronavirus disease 2019 (COVID-19) pandemic. Consistent with the established epidemiological pattern of RSV, the majority of cases in our pre-pandemic cohort (2012–2019) were observed in infants aged 0–11 months. However, during the pandemic period (2020–2023), we noted a substantial increase in the proportion of RSV infections in children aged 2–3 years. This phenomenon, often referred to as “immunological debt,” has been similarly observed in several other countries, suggesting a potential global trend [6,7]. This pattern is consistent with Korean nationwide sentinel surveillance data showing that, after the 2020–2021 absence of RSV circulation, RSV re-emerged in the 2021–2022 season with a delayed and altered seasonality, peaking in January 2022 at a weekly positivity rate of 61% [8].
The underlying mechanism for this shift is likely multifactorial. Public health measures implemented to curb the spread of COVID-19, such as social distancing and mask-wearing, inadvertently reduced transmission of other respiratory viruses, including RSV [9]. This, in turn, led to a larger cohort of children with limited prior exposure to RSV, resulting in increased susceptibility among older age groups when restrictions eased [10]. Awareness of this shift, and possible adjustment of prophylactic strategies for infants in the post-pandemic landscape, may therefore be warranted [11].
Our findings shows the descriptive association between underlying medical conditions and a higher within-group proportion of children who received oxygen therapy or mechanical ventilation. This observation aligns with existing literature that consistently identifies these conditions as significant risk factors for severe RSV disease [12]. The presence of these vulnerable groups in our study population emphasizes the importance of prioritizing and implementing preventive strategies, such as nirsevimab prophylaxis, for these high-risk infants [13]. Consistent with our findings, a recent single-center Korean study during the 2022-2023 season reported that 84.3% of 235 RSV-positive children were hospitalized and 43.4% required oxygen therapy, with underlying disease significantly associated with severity [14]. A recent Korean review highlighted that long-acting monoclonal antibodies such as nirsevimab and maternal RSV vaccines now extend protection to healthy term and late-preterm infants beyond the narrow palivizumab indication, marking a shift in the prevention landscape relevant to our cohort [15].
Within our hospital-based cohort, full-term infants without documented underlying conditions accounted for the largest share of children who received oxygen therapy or mechanical ventilation. This composition primarily reflects the demographic structure of RSV-positive children presenting to referral hospitals, rather than enriched within-group risk. Preterm birth was statistically more frequent among children who received oxygen therapy or mechanical ventilation, but the absolute numbers were very small (22 and 3 children, respectively), so this finding does not alter the observation that severe cases were numerically dominated by full-term infants. During the study period, prophylaxis was restricted to high-risk infants under the national reimbursement framework [16]. Since the 2025–2026 RSV season, long-acting monoclonal antibody has been recommended for all neonates born during the RSV season and for all infants younger than 6 months at the start of the season; our findings, which derive from the targeted-prophylaxis era, should be interpreted in this evolving policy context [15]. These descriptive observations are hypothesis-generating and suggest that broader prevention strategies, such as maternal vaccination or long-acting monoclonal antibodies, may warrant further evaluation alongside targeted prophylaxis. Population-based studies with community comparators and formal cost-effectiveness analyses are needed before stronger conclusions can be drawn.
This study is subject to several limitations inherent to its retrospective design. The reliance on electronic medical records introduces the possibility of selection bias and missing data. Because analyses were performed within a federated OMOP-CDM environment that returned aggregated counts from each of the 21 sites, we could not pool patient-level data to fit multivariable logistic regression models. Reported associations are descriptive and unadjusted, and should not be interpreted as independent risk estimates. Additionally, as the data were sourced from referral hospitals, the study population may not be fully representative of the entire spectrum of RSV infection severity in Korean children. Statements regarding broader prevention strategy should be interpreted as hypothesis-generating rather than as policy recommendations. Our findings should be interpreted as describing the clinical characteristics of RSV-positive children who presented to referral hospitals, and not as estimates of national incidence, absolute risk, or community burden. Without a population denominator and without community-managed cases, incidence by risk group cannot be derived from these data. We were unable to stratify infants into <6 months versus 6–11 months because age was extracted at the 0–11-month level in the federated CDM query. Given that infants <6 months consistently show the highest severity in published cohorts, this is a meaningful limitation, and a follow-up analysis with finer age stratification is planned. Palivizumab use is almost certainly under-captured: only 2 children (0.0%) were recorded as receiving prophylaxis, whereas national reimbursement covers eligible high-risk infants. Doses delivered in outpatient or community clinics may not be coded into the hospital CDM, and our number should not be interpreted as the true coverage of palivizumab in Korea. Furthermore, the absence of certain variables in the dataset, such as socioeconomic status and family history, limits our ability to fully explore the complex interplay of factors that may contribute to severe RSV disease.
Despite these limitations, this study possesses several strengths. The large sample size, encompassing data from 21 referral hospitals across Korea, enhances the statistical power and generalizability of our findings. The utilization of the OMOP-CDM ensures a standardized approach to data collection and analysis, minimizing potential biases and facilitating future research collaborations.
In summary, this 11-year multicenter description of RSV-positive children in 21 Korean referral hospitals shows that severe outcomes were concentrated in young infants, while the absolute composition of severe cases mirrored the cohort's predominance of full-term infants without comorbidities. The post-pandemic shift in age distribution shows the need for continued surveillance. Decisions on whether to expand prophylaxis beyond currently targeted groups will require population-based incidence data and formal economic evaluation.
Footnotes
Funding: This study was funded by Sanofi and AstraZeneca.
Conflict of Interest: YHL, YL, JSL, YY, HJY, JWO, JK and EJ declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. YJC received research grant from Sanofi. LB, HK and SC are employees of Sanofi and may hold shares and/or stock options in the company. All authors attest they meet the ICMJE criteria for authorship.
Data sharing statement: The data that support the findings of this study are available from the corresponding author, upon reasonable request.
- Conceptualization: YHL, YL, YJC.
- Data curation: YHL, YL, JSL, SC, EJ.
- Formal analysis: JK, EJ, YHL, YL.
- Funding acquisition: YJC.
- Investigation: YHL, YL, JSL, SC, YY, HJY, JWO.
- Methodology: YHL, YL, YJC, JK, EJ, HJK.
- Project administration: YJC, YHL, YL.
- Resources: YJC, YY, HJY, JWO, LB.
- Software: JK, EJ.
- Supervision: YJC, YY, HJY, JWO, HJK.
- Validation: YHL, YL, YJC, JK, EJ, HJK.
- Visualization: YHL, YL, JK, EJ. Writing –.
- original draft: YHL, YL. Writing –.
- review & editing: YJC, JSL, YY, HJY, JWO, JK, EJ, SC, HJKi, LB.
SUPPLEMENTARY MATERIAL
List of participating institutions (n=21)
References
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Supplementary Materials
List of participating institutions (n=21)