YNHHS encompasses 5 hospitals located across Connecticut and Rhode Island with a combined capacity for 2681 inpatient beds. The participating hospitals work together with YSM which oversees both clinical and nonclinical faculty. All sites use Epic as the joint EHR for documentation of clinical care issues.

The Clinical and Translational Research Accelerator (CTRA) team at Yale DOM, comprised of physicians and scientists committed to patient-oriented research and developing solutions in clinical medicine, designed the foundation for the database that led to the development of DOM-CovX. CTRA was initially developed in the Section of Nephrology and early data collection focused on renal manifestations of hospitalized COVID-19–positive patients. However, as other departments raised the need for additional data to address their research questions, the CTRA team proposed an expansion of their data collection efforts which was eventually supported by the Yale DOM. This initiative led to the creation of the DOM-CovX core team which provided access to multi-specialty COVID-19 data as well as guidance on the creation of research protocols and analytic plans [9].

Data on COVID-19–positive hospitalized patients were extracted from the EHR using Clarity (Clarity). The cohort was defined as hospitalizations where the patient’s first positive COVID-19 test was documented 14 days preceding admission to the time of discharge. This definition was chosen to be sufficiently sensitive to capture individuals who may have been tested as an outpatient and then presented for hospitalization 1-2 weeks following diagnosis, while also sufficiently specific to exclude patients with recurrent positive swabs, which may not signify new infection but rather nonviable virus with continued polymerase chain reaction positivity. COVID-19 testing within the YNHHS was done by nasopharyngeal swab testing through polymerase chain reaction.

Data across several key domains were extracted, such as demographics, past medical history, laboratory values during hospitalization, vital signs, medications, imaging, procedures (eg, intubation), and outcomes (eg, death, length of stay, and patient disposition). Given the time-varying nature of several data domains, summary statistics were constructed to limit the computational size of the database and provide a reasonable data file that the broader research community could use for basic statistical analyses. To compress each hospitalization to “one-row-per-patient,” summary statistics were calculated for the time-varying data domains with continuous values, which included vital signs and laboratory values from the respective patient. Summary statistics included minimum, maximum, mean, median, 25th and 75th percentiles, and standard deviation. Medications and procedures were reported as “ever” and “never”; for example, if a patient ever received tocilizumab during hospitalization, the variable would read as a “1” or “0”, respectively.

The process for accessing the DOM-CovX Data Explorer (web-based platform) and Repository (master data set) is shown in Figure 1. Researchers who wanted to pursue further study had the opportunity to explore a detailed data dictionary to facilitate understanding and transparency of data in the web-based platform and were offered an online form (Multimedia Appendix 1) to request specific data elements from the DOM-CovX Repository as well as information on the population, exposure, outcome of interest, and hypothesis being tested. A core DOM-CovX team consisting of various representatives from the clinical faculty, informatics department, data scientists, statisticians, and research coordinators reviewed the application and assisted in the process. If the team recognized any potential for collaboration between departments and research groups doing similar or related projects, a dialogue would be facilitated.

Researchers interested in using the DOM-CovX Repository used this algorithm to gain access. Key steps include initial submission to the Yale University institutional review board (IRB), completion of the online DOM-CovX request form, and review of the application by the DOM-CovX team. Requests for new data variables and collaborations were also part of the review. Once the application was accepted, access was granted to a Secure Box folder, a HIPAA (Health Insurance Portability and Accountability Act)-compliant cloud-based file management system used at Yale for data distribution.

Once the application was approved by the core DOM-CovX team, data were distributed to researchers through Secure Box. Data were left in raw format and used by researchers on a variety of statistical software packages for analysis. Biostatistical analysis was left to the individual researchers but in case they would need any assistance with the process, help would be provided by the DOM-CovX team. The analysis process could include merging of DOM-CovX data to another data collection and analytical systems, such as REDCap (Research Electronic Data Capture; Vanderbilt University), a browser-based metadata-driven software to collect and store data for clinical and translational research [10,11]. Researchers had the option of requesting additional data elements from the DOM-CovX team as well as engaging in manual data extraction for fields that were not amenable to computerized data transfer; these additional data elements were also added to the master data set. A master file for all requests and data provisions was maintained and monitored to determine any potential for facilitating collaborations. The DOM-CovX team also tracked resulting presentations, publications, and other academic productivity.

A unique feature of this initiative was the DOM-CovX Explorer, a web-based app designed to provide investigators with a front-end interface to view and inspect variables, see summary statistics, and receive additional information about cohort design and data requests. It was constructed using R Shiny (R Foundation for Statistical Computing) and the statistical visualizations included single variable analyses, scatter plots, box plots, as well as 2×2 tables as shown in Figure 2. Yale researchers have been able to openly explore the data to assess if they are interested in further in-depth study that requires access to the data repository.

A preapproved Human Investigations Committee number and a Yale IRB protocol were required to be uploaded at the time of data request. In case researchers did not have approval yet, the explorer offered a downloadable Yale IRB template for guidance and rapid institutional approval of research protocols. The Yale IRB reviews proposed studies regarding the need for informed consent and this is detailed in the separate process for access to DOM-CovX. Specifically, for secondary data analyses, the IRB grants waivers in line with specific criteria. The IRB application process also details candidates’ compensation when relevant.

For the repository, data were deidentified to remove protected health information as per the HIPAA Security Rule. All dates more specific than year were removed including admission and discharge dates and times, timing of vital signs, laboratory measurements, procedures, or medication administrations. Ages greater than 90 years were set to 90 as per the HIPAA Security Rule. This initiative was reviewed and approved by the Yale IRB (Protocol ID 2000028509)

Since its creation, the DOM-CovX team has received 38 requests from different groups of scientists at Yale to access the database with their research and clinical teams. Most of the requests occurred during the first wave of the pandemic; however, the team has continued receiving at least 1 request every 2-3 months until the present.

Since its creation, the database has included more than 3000 clinically relevant data elements such as demographics, laboratory values, past medical history, vital signs, and medications. The database covers the vast majority of EHR data variables, including specifics of disease stages (eg, acute kidney injury stage 1, 2, and 3), distribution of data elements (eg, mean, mode, median, SD, and IQRs), as well as the addition of data elements generated by automated data extraction or chart review as requested by researchers. The database is regularly updated in a monthly fashion and since July 2020, it has expanded to include 18,828 inpatient encounters, with up to 3997 variables across 7 different clinical domains, which includes added variables related to the hospitalization (eg, length of stay and type of hospital unit).

The DOM-CovX Data Explorer and Repository have been easily accessed and completely free of charge to all Yale faculty and trainees who may otherwise lack independent grant funding and staff to pursue data repository creation. The DOM-CovX has been used by 15 different specialties within the Internal Medicine department, as well as other departments such as Anesthesiology, Neurology, Obstetrics and Gynecology, Pathology, Radiology, and Surgery. Out of the total data requests that we have received, 79% (30/38) have been from different nonsurgical specialties and 21% (8/38) from different surgical specialties (Multimedia Appendix 2). The database has been used to address diverse questions, such as (1) the impact of obesity and diabetes [12], (2) the association of acute kidney injury with COVID-19 [13], (3) the role of neutrophil activation signature in predicting critical illness and mortality in COVID-19 [14], and (4) the association of HIV with COVID-19 outcomes [15].

The simplicity of data request and acquisition, and encouragement to collaborate with established faculty have allowed early career trainees to formulate hypotheses, receive timely access to the repository, and receive mentorship in different areas of interest (Multimedia Appendix 3). The range of users of the database has included 57% (39/68) individuals in a faculty position, 19% (13/68) clinical trainees, 7% (5/68) students, and 16% (11/68) individuals in other research positions.

Multiple collaborations between different departments have been made, bringing together researchers from Cardiology, Emergency Medicine, Endocrinology, Hematology, and Oncology. From January 2020 to January 2023, 18 papers (16 peer-reviewed and 2 in preprints) were published using DOM-CovX data, and 8 abstracts were accepted for presentation in different scientific conferences (Multimedia Appendix 4).

The Yale DOM-CovX, an innovative platform with data from hospitalized patients with COVID-19 in the YNHHS, has been extensively used for a wide range of scholarly productivity during the recent pandemic. It has promoted interdepartmental collaborations and encouraged early career trainees to receive mentorship through a comprehensive, regularly updated, and easily accessed data set. Data requests have involved 38 different groups of scientists and trainees and have resulted in over 20 publications and scientific conference presentations.

During the COVID-19 pandemic, there has been an increase in the availability of open-access data. Clinicians and researchers have been able to access online data trackers from Johns Hopkins, the CDC COVID data tracker, ClinicalTrials.gov website, and local health departments [16-18]. Some of these databases offer summarized information on case trends, demographics, vaccinations, and other outcomes; however, specific clinically relevant and individual patient-level data are often lacking [19,20]. Larger national and international databases with clinical data such as the National COVID Cohort Collaborative (N3C) created and maintained by the National Institutes of Health (NIH), the Infectious Diseases Data Observatory (IDDO), and the International Severe Acute Respiratory and Emerging Infection Consortium (ISARIC) are available, but access can be restricted [21-24]. Local proprietary databases, such as the COVID-19–specific Johns Hopkins Crown Registry (JH-CROWN), use a precision medicine analytics platform that aims to distribute data to institutional investigators [25-27]. Researchers have also created large-scale data repositories for COVID-19 including an alternative COVID-19 clinical data repository curated through the Observational Medical Outcomes Partnership (OMOP) initiative [28,29]. However, these repositories are primarily accessible to large research teams that have the expertise of exploring and analyzing intricated data sets and can present logistic barriers for other faculty and trainees who do not have access to it. In contrast, one significant advantage of the comprehensive DOM-CovX is the availability of detailed clinical variables from hospitalized patients with COVID-19 within our geographic location. Locally relevant research that has significant community impact can be made accessible.

Facilitating the research process is another major benefit of the DOM-CovX Explorer. This website allows the inspection of variables, an easy application process to access as well as support in project design and data analysis if needed. This leads us to one of the lessons learned from the development of this initiative. The use of internal resources facilitates prompt access to data and gives us the flexibility to generate timely changes to the data set if needed. We encourage institutions and their researchers to invest in internal resources considering how responsive these are to local needs and further input. Currently, access is offered to all Yale clinicians and researchers and potential expansion of its availability to researchers outside the institution is being considered. This new step could lead the way to institutional collaborations within and outside the United States to continue evaluating the epidemiology of the COVID-19 pandemic.

We anticipate that as the process evolves, there will be a growing impact on medical education and scientific productivity involving researchers in different stages of training like we have evidenced locally. Specifically, the rapidly changing academic landscape requires that curricula provide the intellectual currency for all trainees and faculty to critically understand the explosion of clinical and research literature including the optimal use of data and recognition of its limitations. Inequities of data access may result in a more divided group of learners with narrower expectations and rewards. DOM-CovX presents a basis for further generation of databases or repositories focused on bridging the intellectual divide and expanding the scope and quality of medical education. Thus, another lesson learned is the importance of establishing strategies to promote access to the resources that expand knowledge and promote education. For DOM-CovX, these strategies are an ongoing effort that aims to secure the sustainability of this initiative and promote its constant growth.

Currently, tools for statistical analysis have not yet been built into the workflow. Nonetheless, future goals could incorporate access to fundamental analytic tools and statisticians, improve training and mentoring of clinician-educators, and aid clinicians to engage in fundamental understanding of research analytics as well as to improve data management skills. The open access of DOM-CovX could also improve the implementation of available analytic resources. Zanettini et al [30] presented one possibility with the COVID-19 census, an R package that retrieves different repositories and databases from the United States and Italy, creating a combined set of metrics and other demographic variables, to facilitate multivariable analysis and modeling by the scientific community.

Limitations of the DOM-CovX Repository are inclusion only of data on hospitalized patients. The database focuses only on clinical data and does not lend itself to studies requiring a biorepository.

The Yale DOM-CovX Data Explorer and repository have provided an accessible tool for simple data analysis and access to a consistently updated, standardized, and large-scale database for patients hospitalized with COVID-19 in our hospital system. It overcomes barriers for a wide variety of researchers and has demonstrated the potential to increase academic productivity. It represents an opportunity to improve the institutional climate by fostering collaboration and diversity of scholarly pursuits.