A Study to Learn How Paxlovid [Nirmatrelvir-ritonavir/PF-07321332] Works in COVID-19 Patients Who Are Elderly or Have Medical Conditions.

NCT07261085 | Active Not Recruiting FDA Drug

• 1 other identifier: C4671071
• Study Type: observational
• Target: 99,000
• Locations: 1 country
• Sites: 1

Brief Summary

The purpose of this study is to learn about the effects of the study medicine called Paxlovid \[nirmatrelvir-ritonavir/PF-07321332\], for the potential treatment of COVID-19. This study will use patient health records in Ontario, to find people who were sick with COVID-19 and visited a pharmacist to be treated, anytime from December 1st, 2022, to March 31st, 2024. To be included in our study, the people must be over 18 years of age and be registered in the Ontario health system for at least one year. People were not included in our study if they have been pregnant in the past year or have serious kidney or liver disease. We will separate the people in the study into two groups: those who received treatment with Paxlovid \[nirmatrelvir-ritonavir/PF-07321332\] and those who received no treatment. We will monitor their healthcare visits or if they die for any reason, for up to 60 days after the date that they visited their pharmacist. Then we will compare participant experiences when they are taking the study medicine to when they are not. This will help us determine if the study medicine is effective.

Conditions

COVID-19

Keywords

Covid-19; SARS-COV2

Outcome Measures

Primary Outcomes (1)

• Time to the first severe composite outcome (all-cause hospital admission, ICU admission, or death) within 30 days of treatment assessment.

  Participants selected between 01 Dec, 2022 to 31 March 2024

Secondary Outcomes (1)

• Time to the first severe composite outcome (all-cause hospital admission, ICU admission, or death) within 60 days of treatment assessment.

  Participants selected between 01 Dec, 2022 to 31 March 2024

Study Arms (2)

Assessed and Treated Cohort

Participants who were assessed with Covid prescribed and subsequently dispensed nirmatrelvir-ritonavir during the selection period

Drug: nirmatrelvir-ritonavir

Assessed and Untreated Cohort

Participants who were assessed with Covid for nirmatrelvir-ritonavir but either were not prescribed the medication or did not have it dispensed during the selection period

Other: No treatment

Interventions

No treatment OTHER

Participants who were assessed with Covid for nirmatrelvir-ritonavir but either were not prescribed the medication or did not have it dispensed during the selection period

Assessed and Untreated Cohort

nirmatrelvir-ritonavir DRUG

Participants who were assessed with Covid prescribed and subsequently dispensed nirmatrelvir-ritonavir during the selection period

Also known as: paxlovid

Assessed and Treated Cohort

Eligibility Criteria

• Age: 18 Years+
• Sex: all
• Healthy Volunteers: No
• Age Groups: Adult (18-64), Older Adult (65+)
• Sampling Method: Non-Probability Sample

Study Population

The Institute for Clinical Evaluative Sciences (ICES) data repository consists of de-identified, record-level, coded and linkable health data sets. It encompasses much of the publicly funded administrative health services records for the Ontario population eligible for universal health coverage since 1986 and integrates administrative data, registries, and surveys.

You may qualify if:

• Record of at least 1 nirmatrelvir-ritonavir prescription and at least 1 dispensation issued by the pharmacist (Treated Cohort only) within 5 days of prescription, identified through pharmacy billing codes
• Record of at least 1 assessment for nirmatrelvir-ritonavir, without a prescription issued by the pharmacist (Untreated Cohort only), OR record of at least 1 prescription for nirmatrelvir-ritonavir without dispensation (Untreated Cohort only), identified through pharmacy billing codes

You may not qualify if:

• Invalid or incomplete records (e.g., missing age, missing sex, death before index)
• Record of a positive PCR test for SARS-CoV-2 between 5 and 90 days prior to the index date
• Had a prescription for antivirals within 3 days prior to or on the index date

Sponsors & Collaborators

• Pfizer: lead

Study Sites (1)

Pfizer New York

New York, New York, 10001, United States

Location

Related Links

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

MeSH Terms

Conditions

COVID-19

Interventions

nirmatrelvir and ritonavir drug combination

Condition Hierarchy (Ancestors)

Pneumonia, Viral; Pneumonia; Respiratory Tract Infections; Infections; Virus Diseases; Coronavirus Infections; Coronaviridae Infections; Nidovirales Infections; RNA Virus Infections; Lung Diseases; Respiratory Tract Diseases

Study Officials

• Pfizer CT.gov Call Center

  Pfizer

  STUDY DIRECTOR

Study Design

• Study Type: observational
• Observational Model: COHORT
• Time Perspective: RETROSPECTIVE
• Sponsor Type: INDUSTRY
• Responsible Party: SPONSOR

Study Record Dates

• First Submitted: November 21, 2025
• First Posted: December 3, 2025
• Study Start: October 27, 2025
• Primary Completion: March 30, 2026
• Study Completion: March 30, 2026
• Last Updated: December 4, 2025

Record last verified: 2025-12

Data Sharing

• IPD Sharing: Will not share

Locations

US (1)