A Study to Learn About PAXLOVID (a Commercial Medicine) In People With COVID-19

General Investigation for PAXLOVID PAC

The purpose of this post marketing observational study is to learn about the safety and effects of the commercial medicine (called PAXLOVID) for the treatment of COVID-19. This study is intended to be registered with the participants who:

• Have taken PAXLOVID PACK and have no history of using this medicine.
• Are 12 years and older

All participants will receive PAXLOVID, a standard treatment for COVID-19. Participants will take PAXLOVID 2 times a day by mouth or as prescribed.

We will examine the experiences of people taking PAXLOVID. This will help us determine if PAXLOVID is safe and effective.

Participants will be followed up for 28 days after taking PAXLOVID. During this time, participants will be closely watched for the safety and effects of PAXLOVID.

Study Overview

• Status: Completed
• Conditions: SARS-CoV-2 Infection
• Intervention / Treatment: Drug: nirmatrelvir / ritonavir

Detailed Description

This is a multicenter cohort study to be conducted in individuals with SARS-CoV-2 infection who are treated with this product, and the investigator will enter the information required in this study in the case report forms (CRFs) based on the information obtained through medical records.

• Study Type: Observational
• Enrollment (Actual): 3346

Contacts and Locations

Study Locations

• Japan
  • Tokyo, Japan, 1518589
    • Pfizer Local County

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 12 years and older (Child, Adult, Older Adult)
• Accepts Healthy Volunteers: No

• Sampling Method: Probability Sample

Study Population

The subjects who have been treated with PAXLOVID PACK for the first time.

Description

Inclusion Criteria:

• Subjects who are administered PAXLOVID PACK and have no history of using this drug.

Exclusion Criteria:

• There are no exclusion criteria for this study.

Study Plan

How is the study designed?

Design Details

• Observational Models: Case-Only
• Time Perspectives: Prospective

Number of groups / cohorts

1

Cohorts and Interventions

Group / Cohort	Intervention / Treatment
PAXLOVID PACK; Subjects administered PAXLOVID PACK	Drug: nirmatrelvir / ritonavir; The usual dosage in adults and pediatric patients (≥12 years of age weighing ≥40 kg) is 300 mg of Nirmatrelvir and 100 mg of ritonavir all taken together orally twice daily for 5 days.; Other Names: PAXLOVID PACK

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Incidence of Adverse Drug Reactions	Adverse drug reaction (ADR) was a treatment-related adverse event and any untoward medical occurrence attributed to Paxlovid PACK in a participant who received Paxlovid PACK. Serious adverse drug reaction (SADR) was a treatment-related adverse event resulting in any of the following outcomes or deemed significant for any other reason: death; life-threatening; initial or prolonged inpatient hospitalization; persistent or significant disability/incapacity; congenital anomaly/birth defect. Relatedness to Paxlovid PACK was assessed by the physician.	From the start date of treatment with Paxlovid PACK to 28 days after the end of treatment, up to approximately 45 days.

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Percentage of Participants With Worsening Severity (Efficacy Analysis Set #1)	Whether the severity of infection caused by SARS-CoV-2 had worsened was evaluated. However, when the severity was severe at the start of Paxlovid PACK and did not worsen during the observation period, it was considered as "severe at the start of treatment."	From the start date of treatment with Paxlovid PACK to 28 days after the end of treatment, up to approximately 45 days.
Percentage of Participants With Worsening Severity (Efficacy Analysis Set #2)	Whether the severity of infection caused by SARS-CoV-2 had worsened was evaluated. However, when the severity was severe at the start of Paxlovid PACK and did not worsen during the observation period, it was considered as "severe at the start of treatment."	From the start date of treatment with Paxlovid PACK to 28 days after the end of treatment, up to approximately 35 days.
Percentage of Participants With Worsening Severity (Efficacy Analysis Set #3)	Whether the severity of infection caused by SARS-CoV-2 had worsened was evaluated. However, when the severity was severe at the start of Paxlovid PACK and did not worsen during the observation period, it was considered as "severe at the start of treatment."	From the start date of treatment with Paxlovid PACK to 28 days after the end of treatment, up to approximately 35 days.
Cumulative Incidence Rate of COVID-19 Related Hospitalization or Death From Any Cause Through Day 28 (Efficacy Analysis Set #3)	The percent probability is the percent of the participants who had COVID-19 related hospitalization or death from any cause.	3, 5, 7, 14, 21 and 28 days after the start of administration with Paxlovid PACK.
Cumulative Incidence Rate of COVID-19 Related Hospitalization or Death From Any Cause Through Day 28 (Sensitivity Analysis) (Efficacy Analysis Set #3)	The percent probability is the percent of the participants who had COVID-19 related hospitalization or death from any cause. Sensitivity analysis was conducted by changing the event definition of "hospitalization for treatment of infection caused by SARS-CoV-2" as follows: there were concomitant medications for infection caused by SARS-CoV-2 or concomitant non-drug therapies due to infection caused by SARS-CoV-2 on or after the date of administration.	3, 5, 7, 14, 21 and 28 days after the start of administration with Paxlovid PACK.

Collaborators and Investigators

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

Publications and helpful links

Helpful Links

• To obtain contact information for a study center near you, click here.

Study record dates

Study Major Dates

• Study Start (Actual): March 31, 2022
• Primary Completion (Actual): July 10, 2023
• Study Completion (Actual): July 10, 2023

Study Registration Dates

• First Submitted: February 25, 2022
• First Submitted That Met QC Criteria: February 25, 2022
• First Posted (Actual): March 3, 2022

Study Record Updates

• Last Update Posted (Estimated): September 3, 2025
• Last Update Submitted That Met QC Criteria: August 13, 2025
• Last Verified: August 1, 2025

More Information

Terms related to this study

• Keywords: Paxlovid; Nirmatrelvir; severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2); coronavirus disease 2019 (COVID-19)
• 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; Molecular Mechanisms of Pharmacological Action; Anti-Infective Agents; Antiviral Agents; Enzyme Inhibitors; Anti-HIV Agents; Anti-Retroviral Agents; Protease Inhibitors; Cytochrome P-450 CYP3A Inhibitors; Cytochrome P-450 Enzyme Inhibitors; HIV Protease Inhibitors; Viral Protease Inhibitors; nirmatrelvir and ritonavir drug combination
• Other Study ID Numbers: C4671018; NCT05263908 (Registry Identifier: ClinicalTrials.gov)

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: No
• Studies a U.S. FDA-regulated device product: No
• product manufactured in and exported from the U.S.: No