A Study to Learn About the Study Medicine Paxlovid (Nirmatrelvir + Ritonavir) in Adults Aged 60 and Older Living in Korean Long-term Care Hospitals Who Have COVID-19

Impact of Nirmatrelvir and Ritonavir (PAXLOVID®) on Mortality, Progression to Severe Disease, and Activities of Daily Living (ADL) Worsening in Long-term Care Hospitals (LTCHs) in Korea

The purpose of this study is to learn about the effects of the study medicine (called Paxlovid) for the possible treatment of COVID-19 in older adults who live in long-term care hospitals (LTCHs) in Korea. Researchers want to know whether Paxlovid lowers the chance of severe illness or death and helps people carry out their usual daily activities, remain free from aging and weakness, and maintain cognitive function.

This study is seeking participants who:

• are 60 years of age or older
• live in a long-term care hospital in Korea
• were diagnosed with COVID-19 on or after 14 January 2022, during the period when Paxlovid was available as part of routine care
• received Paxlovid within 5 days after their first COVID-19 symptoms (only for people in the Paxlovid group)

All participants in this study received their usual COVID-19 care. About half also received Paxlovid. Paxlovid was prescribed as part of routine care at the long-term care hospital, typically taken by mouth 2 times a day for 5 days.

The study team will compare the health results of people who received Paxlovid to those who did not, using similar parameters such as age, sex, and medical history. This will help the study team to understand whether Paxlovid makes a meaningful difference in stopping severe illness, death, or slow-down daily functioning.

Participants will not have any extra study visits or tests. The study team will only review information already recorded in their medical charts for up to 1 year after their COVID-19 symptom onset.

Study Overview

• Status: Not yet recruiting
• Conditions: Coronavirus Disease 2019 (COVID-19)
• Intervention / Treatment: Drug: Nirmatrelvir/Ritonavir

• Study Type: Observational
• Enrollment (Estimated): 1200

Contacts and Locations

• Study Contact: Name: Pfizer CT.gov Call Center; Phone Number: 1-800-718-1021; Email: ClinicalTrials.gov_Inquiries@pfizer.com

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: No

• Sampling Method: Non-Probability Sample

Study Population

The study population includes residents of long-term care hospitals (LTCHs) in Korea who are aged 60 years or older and were diagnosed with COVID-19 between January 14, 2022 and June 1, 2023 (or latest available date). Diagnosis was confirmed by SARS-CoV-2 PCR or antigen test, and symptom onset date was available. Participants were either treated with Paxlovid (Nirmatrelvir/Ritonavir) within 5 days of symptom onset or received no antiviral treatment. Patients were excluded if they received other COVID-19 treatments (e.g., remdesivir, molnupiravir, monoclonal antibodies), had severe renal or hepatic dysfunction, or had contraindicated medications. The study uses retrospective medical chart data and includes follow-up for up to 365 days.

Description

1. LTCH residents ≥60 years of age, diagnosed with COVID-19 via SARS-CoV-2 PCR or antigen test, with a symptom onset date (index date) between 14 January 2022 and 1 June 2023 (or latest date available)
2. Dispensed Paxlovid within 5 days of COVID-19 symptom onset (Paxlovid treated patients only)

Study Plan

How is the study designed?

Number of groups / cohorts

2

Cohorts and Interventions

Group / Cohort	Intervention / Treatment
Paxlovid treated group; Participants aged 60 years or older residing in long-term care hospitals (LTCHs) in Korea who were diagnosed with COVID-19 and received Paxlovid (Nirmatrelvir/Ritonavir) as part of their clinical care. This group will be assessed for multiple outcomes including mortality, progression to severe disease, worsening of activities of daily living (ADL), and frailty.	Drug: Nirmatrelvir/Ritonavir; Participants aged 60 years or older residing in long-term care hospitals (LTCHs) in Korea who were diagnosed with COVID-19 and received Paxlovid (Nirmatrelvir/Ritonavir) as part of their clinical care. This group will be assessed for multiple outcomes including mortality, progression to severe disease, worsening of activities of daily living (ADL), and frailty.; Other Names: Paxlovid
Paxlovid untreated group; Participants aged 60 years or older residing in long-term care hospitals (LTCHs) in Korea who were diagnosed with COVID-19 but did not receive Paxlovid treatment. This group serves as a comparator to evaluate the effectiveness of Paxlovid on outcomes such as mortality, progression to severe disease, ADL decline, and frailty.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Time Frame
Composite outcome of progression to severe disease or all-cause mortality within 30 days	During index date, defined as 30 days from COVID-19 symptom onset. Index period: 14 Jan 2022 to 1 June 2025 (or latest date available)

Secondary Outcome Measures

Outcome Measure	Time Frame
Change in Activities of Daily Living (ADL) from baseline at 30 days	During index date, defined as 30 days from COVID-19 symptom onset. Index period: 14 Jan 2022 to 1 June 2025 (or latest date available)
Change in Activities of Daily Living (ADL) from baseline at 90 days	During index date, defined as 30 days from COVID-19 symptom onset. Index period: 14 Jan 2022 to 1 June 2025 (or latest date available)
Change in Activities of Daily Living (ADL) from baseline at 365 days	During index date, defined as 30 days from COVID-19 symptom onset. Index period: 14 Jan 2022 to 1 June 2025 (or latest date available)
All Cause mortality at 30 days by baseline ADL dependency	During index date, defined as 30 days from COVID-19 symptom onset. Index period: 14 Jan 2022 to 1 June 2025 (or latest date available)
Progression to severe disease at 30 days by baseline ADL dependency	During index date, defined as 30 days from COVID-19 symptom onset. Index period: 14 Jan 2022 to 1 June 2025 (or latest date available)
ADL change at 30 days by baseline ADL dependency	During index date, defined as 30 days from COVID-19 symptom onset. Index period: 14 Jan 2022 to 1 June 2025 (or latest date available)
Subgroup analysis of ADL change at 90 days by baseline ADL dependency	During index date, defined as 30 days from COVID-19 symptom onset. Index period: 14 Jan 2022 to 1 June 2025 (or latest date available)
Subgroup analysis of ADL change at 365 days by baseline ADL dependency	During index date, defined as 30 days from COVID-19 symptom onset. Index period: 14 Jan 2022 to 1 June 2025 (or latest date available)

Collaborators and Investigators

• Sponsor: Pfizer
• Investigators: Study Director: Pfizer CT.gov Call Center, Pfizer

Study record dates

Study Major Dates

• Study Start (Estimated): August 18, 2025
• Primary Completion (Estimated): November 30, 2025
• Study Completion (Estimated): November 30, 2025

Study Registration Dates

• First Submitted: July 24, 2025
• First Submitted That Met QC Criteria: July 24, 2025
• First Posted (Actual): July 28, 2025

Study Record Updates

• Last Update Posted (Actual): July 28, 2025
• Last Update Submitted That Met QC Criteria: July 24, 2025
• Last Verified: July 1, 2025

More Information

Terms related to this study

• Keywords: COVID-19; Frailty; Activities of Daily Living (ADL); Nirmatrelvir / Ritonavir (Paxlovid); Long-Term Care Hospitals
• Additional Relevant MeSH Terms: Respiratory Tract Infections; Infections; RNA Virus Infections; Virus Diseases; Respiratory Tract Diseases; Lung Diseases; Pneumonia, Viral; Pneumonia; Coronavirus Infections; Coronaviridae Infections; Nidovirales Infections; COVID-19; Viral Protease Inhibitors; Anti-Infective Agents; Molecular Mechanisms of Pharmacological Action; Protease Inhibitors; Enzyme Inhibitors; Antiviral Agents; Cytochrome P-450 Enzyme Inhibitors; Anti-HIV Agents; Anti-Retroviral Agents; HIV Protease Inhibitors; Cytochrome P-450 CYP3A Inhibitors; Nirmatrelvir; Nirmatrelvir and ritonavir drug combination; Ritonavir
• Other Study ID Numbers: C4671064

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO
• IPD Plan Description: Pfizer will provide access to individual de-identified participant data and related study documents (e.g. protocol, Statistical Analysis Plan (SAP), Clinical Study Report (CSR)) upon request from qualified researchers, and subject to certain criteria, conditions, and exceptions. Further details on Pfizer's data sharing criteria and process for requesting access can be found at: https://www.pfizer.com/science/clinical_trials/trial_data_and_results/data_requests.

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: Yes
• Studies a U.S. FDA-regulated device product: No