An observational study in COVID-19, SARS-CoV-2 Infection, RSV and Influenza, sponsored by VA Office of Research and Development. Recruiting at 1 site in United States. Open to participants aged 18 Years and older, including healthy volunteers. Per ClinicalTrials.gov, last updated 2026-09-30.
Sponsored by VA Office of Research and Development · Observational
The purpose of this study is to comprehensively describe the temporal and geographic utilization of COVID-19 therapies used for mild to moderate disease during different periods of SARS-CoV-2 variant circulation as well as to compare demographic and clinical characteristics of Veterans who are treated or do not receive these different therapies. The investigators will also perform similar descriptive epidemiology for other respiratory viruses, including RSV and influenza and other infectious diseases. This first phase will critically inform feasibility and direction of the second phase, in which the investigators will use target trial emulation design to study the comparative effectiveness of therapies and vaccines for COVID-19, respiratory viruses, including RSV, and influenza, and other infectious diseases.
Objectives:
This study will be completed in two phases. In the first phase, the investigators will establish a source population and comprehensively describe the temporal and geographic utilization of COVID-19 pharmacotherapies beginning July 2021. These therapies include casirivimab and imdevimab, bamlanivimab and etesevimab, sotrovimab, nirmatrelvir, molnupiravir, and remdesivir. The investigators will also compare demographic and clinical characteristics of Veterans who are treated or do not receive these therapies. Phase 1 will inform the study design and analytic protocol of Phase 2. Phase 1 will also inform critical policy questions and national guidance regarding COVID-19 pharmacotherapies in the VA healthcare system with the potential to inform policy across other healthcare systems.
In the second phase, the investigators will conduct target trial emulation studies to determine the effectiveness and comparative effectiveness of current pharmacotherapies for COVID-19 in preventing short- and long-term adverse outcomes related to SARS-CoV-2 infection. The investigators will use a sequence of comparative effectiveness studies through emulation to help establish a common framework sharing a similar population, design, and outcomes for a rapid-response, adaptive observational study design to characterize utilization and determine the effectiveness and comparative effectiveness of novel therapeutic agents authorized for the treatment of mild to moderate COVID-19 in Veterans. Phase 2 will provide an infrastructure upon which subsequent observational studies can be performed, which will include other infectious diseases of interest, ultimately ensuring the timeliness and pertinence of VA research.
Research Design and Methodology:
In the first phase, the investigators will conduct a descriptive, retrospective, electronic health record-based study among Veterans aged 18 years with a laboratory-confirmed positive test for SARS-CoV-2 or a diagnosis of COVID-19 documented at any time since the beginning of the pandemic in January 2020 to present. The investigators will describe the geographic distribution (by VISN, state, and distance from place of residence to the closest VAMC and/ COVID-19 infusion facilities) of Veterans receiving each of the COVID-19 antiviral and monoclonal antibody therapies during different periods of SARS-CoV-2 variant circulation (i.e., January 1, 2022, to present for Omicron). The investigators will also compare baseline demographic characteristics, clinical characteristics including underlying medical conditions and prior SARS-CoV-2 infections, SARS-CoV-2 vaccination status, National Institutes of Health (NIH) risk group tiers for prioritization of treatments, concurrent outpatient medications, and time from positive test to treatment among Veterans receiving different antiviral and monoclonal antibody therapies as well as eligible Veterans who are not treated during different periods of SARS-CoV-2 variant circulation. This established framework will also be used to identify Veterans who tested positive for other respiratory viruses, including influenza virus or respiratory syncytial virus (RSV), and other infectious diseases in the same time period and describe their characteristics, risk factors and treatments.
In the second phase, the investigators will conduct retrospective and prospective target trial emulation studies to evaluate the effectiveness and comparative effectiveness of different pharmacotherapies for mild-to-moderate COVID-19 in patients with documented SARS-CoV-2 infection by period of predominant SARS-CoV-2 variant circulation. The established framework will be used to investigate vaccine and pharmacotherapy effectiveness for SARS-CoV-2 and other respiratory viruses, including influenza and respiratory syncytial virus (RSV) and other infectious diseases using observational data from the VHA electronic health records.
Impact Significance:
Data on real-world utilization and clinical outcomes in the Veteran population are needed to inform clinical, operational and research partners in the VA and other healthcare systems on strategies for optimizing the utilization of pharmacotherapies and vaccines against COVID-19 and other infectious diseases. Ongoing evaluations will be essential as new variants emerge, vaccination practices evolve, and new pharmacotherapies are introduced. This study will establish a common framework sharing a similar population, design, and outcomes for a rapid-response, adaptive platform observational study design to characterize utilization and determine the effectiveness and comparative effectiveness of novel therapeutic agents authorized for the treatment of mild to moderate COVID-19, respiratory viruses, including RSV and influenza, and other infectious diseases in Veterans.
VA enrollees infected from January 1, 2022 through February 28, 2022 as an example. Subsequent trials will be executed as the pandemic evolves
Phase 1:
- Veterans with a laboratory-confirmed positive test for SARS-CoV-2 or a diagnosis of COVID-19 documented at any time since the beginning of the pandemic in January 2020 to present
Phase 2:
Exclusion Criteria:
This cohort study assessed outpatient Veterans with risk factors for severe COVID-19 who tested positive for SARS-CoV-2 during January and February 2022. The purpose is to describe factors associated with receipt of outpatient COVID-19 pharmacotherapies in the Veterans Affairs (VA) health care system.
Three retrospective target trial emulation studies comparing matched cohorts of nirmatrelvir-ritonavir versus no treatment, molnupiravir versus no treatment, and nirmatrelvir- ritonavir versus molnupiravir. The purpose is to measure the effectiveness of nirmatrelvir-ritonavir and molnupiravir for outpatient treatment of COVID-19.
This cohort study evaluated nonhospitalized Veterans in VHA care who tested positive for SARS-CoV-2 from January 2022 through January 2023 using VHA and linked Community Care and Medicare databases. The purpose is to analyze trends and factors associated with prescription of outpatient COVID-19 pharmacotherapies within the Veterans Health Administration (VHA).
Retrospective target trial emulation study comparing matched cohorts receiving nirmatrelvir-ritonavir versus no treatment. The purpose is to measure the effectiveness of outpatient treatment of COVID-19 with nirmatrelvir-ritonavir in preventing Post COVID conditions.
Receipt of any COVID-19 pharmacotherapy, including sotrovimab, nirmatrelvir boosted with ritonavir, molnupiravir, or remdesivir
The odds of receipt of any COVID-19 pharmacotherapy, including sotrovimab, nirmatrelvir boosted with ritonavir, molnupiravir, or remdesivir were estimated using multivariable logistic regression
Time frame: January and February 2022
Incidence of any hospitalization or all-cause mortality at 30 days and from 31 to 180 days
Three retrospective target trial emulation studies comparing matched cohorts of nirmatrelvir-ritonavir versus no treatment, molnupiravir versus no treatment, and nirmatrelvir- ritonavir versus molnupiravir.
Time frame: January through July 2022
Monthly receipt of any COVID-19 pharmacotherapy (nirmatrelvir-ritonavir, molnupiravir, sotrovimab, or bebtelovimab)
To analyze trends and factors associated with prescription of outpatient COVID-19 pharmacotherapies within the Veterans Health Administration (VHA).
Time frame: January 2022 through January 2023
Cumulative incidence of 31 potential PCCs at 31 -180 days after treatment or a matched index date, including cardiac, pulmonary, renal, thromboembolic, gastrointestinal, neurologic, mental health, musculoskeletal, endocrine, and general conditions
Retrospective target trial emulation study comparing matched cohorts receiving nirmatrelvir-ritonavir versus no treatment.
Time frame: January through July 2022
Incidence of any hospitalization or all-cause mortality at 30 days
Target trial emulation study in the Veterans Health Administration comparing nirmatrelvir-ritonavir treated versus matched untreated Veterans at risk for severe COVID-19 who tested positive for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)
Time frame: April 2022 through March 2023
Prediction of 30-day COVID-19 hospitalization and death in the Omicron era for contemporary clinical and research applications
Full models incorporated 84 predictors, including demographics, comorbidities, and receipt of COVID-19 vaccinations and anti-SARS-CoV-2 treatments. Parsimonious models included 19 predictors. The investigators created models for 30-day hospitalization or death, 30-day hospitalization, and 30-day all-cause mortality. The investigators used the Super Learner ensemble machine learning algorithm to fit prediction models. Model performance was assessed with the area under the receiver operating characteristic curve (AUC), Brier scores, and calibration intercepts and slopes in a 20% holdout dataset.
Time frame: March 1, 2022, and March 31, 2023
RSVPreF3 or RSVpreF vaccination compared with no respiratory syncytial virus (RSV) vaccination for the prevention of documented RSV infection and associated health-care use among Veterans
The primary outcome was any positive respiratory syncytial virus (RSV) test result occurring from day 14 following the index date until the end of the study period. Secondary outcomes included RSV-associated emergency department or urgent care encounters, RSV-associated acute hospitalizations, RSV associated intensive care unit (ICU) admissions, and death. RSV-associated health-care encounters were defined as any corresponding encounter occurring the day before until 1 day after the eligible positive RSV test result. Death was defined as any death occurring on the day of until 30 days after the eligible positive RSV test result.
Time frame: March 1, 2022, and March 31, 2023
compare disease severity of COVID-19, influenza, and RSV among US Veterans
This retrospective cohort study analyzed national US Veterans Health Administration electronic health record data of non-hospitalized Veterans who underwent same-day testing for SARS-CoV-2, influenza, and RSV, and were diagnosed with a single infection between August 1, 2022, and March 31, 2023, or between August 1, 2023, and March 31, 2024. Following inverse probability weighting, the cumulative incidence and risk differences (RDs) were calculated for the primary outcomes of 30-day hospitalization, intensive care unit admission, and death, as well as the secondary outcome of long-term death extending through 180 days.
Time frame: August 1, 2022, and March 31, 2023, or between August 1, 2023, and March 31, 2024.
Determine XBB.1.5 COVID-19 vaccine effectiveness (VE) and the extent to which it declines over time
Outcomes were ascertained through 10 May 2024 and included any positive result on a SARS-CoV-2 test from day 10 after the matched index date, subsequent hospitalization within 1 day before or 10 days after the positive result, or death within 30 days after the positive result. Vaccine effectiveness was estimated as 100x (1-risk ratio).
Time frame: October 2,2023- January 3, 2024
Determine if severe SARS-CoV-2 infection increases risk of selected PCCs or death up to 1 year after infection in wild-type (WT), Alpha-transition, Delta, and Omicron eras
Investigated whether severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection increases the risk of selected PCCs or death up to 1 year after infection, separately in the wild-type (WT), Alpha-transition, Delta, and Omicron eras and by vaccination status.
Time frame: March 2020 and April 2022
Determined budget cost of providing nirmatrelvir-ritonavir to Veterans with COVID-19 on 30-day healthcare costs to inform procurement strategies in large healthcare systems
The decision tree analysis included transition states from cohort entry (i.e., infection and treatment) to emergency department (ED) visit, hospitalization without intensive care unit (ICU) admission, hospitalization with ICU admission, recovery, and death. Decision trees were created for each subgroup and treatment allocation and parameterized with subgroup and treatment specific transition probabilities. In total, 26 trees (13 subgroups and 2 treatment scenarios) were created and parameterized with over 150 transition probabilities.
Time frame: April 2022 through March 2023
Evaluate the impact of different time zero designations on results and inferences from a cohort study comparing the effectiveness of nirmatrelvir ritonavir treatment versus no COVID-19 antiviral treatment in preventing 30-day hospitalization and death
Identified US Veterans who tested positive for SARS-CoV-2 from April 2022-March 2023 and compared nirmatrelvir-ritonavir versus no treatment using 5 time zero approaches: test-date (treated) versus test-date (untreated) with matching allowing treatment on days 0-5 (approach 1a) or day 0 only (1b), test-date versus test-date with a clone-censor-weight method (1c), treatment date versus test-date (2) with matching, or treatment date versus matched index date (3).
Time frame: April 2022-March 2023
Asses the long-term effectiveness of a single respiratory syncytial virus (RSV) vaccine dose against RSV illness and associated health care use
The primary outcome was any positive RSV test result from day 14 following the matched index date. Secondary outcomes included RSV-associated emergency department or urgent care visits, hospitalizations, or intensive care unit admissions. Vaccine effectiveness was estimated as 100 × (1 - risk ratio).
Time frame: September 2023 to March 2024.
Estimate the long-term vaccine effectiveness (VE) of the 2024-2025 COVID-19 vaccines targeting the KP.2 Omicron variant within the Veterans Health Administration
Vaccine effectiveness against documented SARS CoV-2 infection, SARS-CoV-2 associated ED/UC visit, SARS-CoV-2 associated hospitalization or SARS-CoV-2 associated death
Time frame: August 1, 2024- April 12, 2025
Compared treatment with oseltamivir versus no antiviral treatment within 6 hours of a positive influenza test
Assessed Veterans who presented to emergency departments in the Veterans Health Administration (VHA) and tested positive for influenza
Time frame: 1 October 2022-31 January 2023; 1 December 2023-31 March 2024
Calculated cumulative incidence, risk differences (RDs), and risk ratios (RR) for hospitalization and intensive care unit (ICU) admission at 10 days
Assessed Veterans who presented to emergency departments in the Veterans Health Administration (VHA) and tested positive for influenza
Time frame: 1 October 2022-31 January 2023; 1 December 2023-31 March 2024
Calculated cumulative incidence, risk differences (RDs), and risk ratios (RR) for hospitalization and intensive care unit (ICU) admission at death at 30 days
Assessed Veterans who presented to emergency departments in the Veterans Health Administration (VHA) and tested positive for influenza
Time frame: 1 October 2022-31 January 2023; 1 December 2023-31 March 2024
Plan to share: No — There is not a plan to make IPD available
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