COVID-19NCT07261085
A Study to Learn How Paxlovid [Nirmatrelvir-ritonavir/PF-07321332] Works in COVID-19 Patients Who Are Elderly or Have Medical Conditions.
An observational study of COVID-19, run by Pfizer at 1 site in United States.
Trial 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… Read more about this study
- Who is it for?
- Ages 18 years and older
- Conditions the study is for
- COVID-19
- What is being tested?
- nirmatrelvir-ritonavir and No treatment
- How many people
- 99,000 participants
- Where
- 1 siteUnited States
- Study dates
- 27 Oct 2025to 26 Feb 2026
- Phase
- Observational
- Are there results?
- None posted in the registry
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 18 years and older
- All sexes
- No healthy volunteers
- Adult, Older adult
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.
Who may be able to join
- 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
Who cannot join
- 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
Trial locations and contacts
1 site in 1 country.
About this study
Official title: A REAL-WORLD STUDY ON THE EFFECTIVENESS OF NIRMATRELVIR-RITONAVIR IN REDUCING SEVERE OUTCOMES FROM COVID-19
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
- Being tested
- nirmatrelvir-ritonavir, No treatment
- Keywords
- Covid-19, SARS-COV2
- Medical subject headings
- COVID-19
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
nirmatrelvir-ritonavirDrug
Also called paxlovid
Participants who were assessed with Covid prescribed and subsequently dispensed nirmatrelvir-ritonavir during the selection period
No treatmentOther
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
| Study group | Role | What they receive |
|---|---|---|
| Assessed and Treated Cohort | Participants who were assessed with Covid prescribed and subsequently dispensed nirmatrelvir-ritonavir during the selection period Receives: 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 Receives: Other: No treatment |
What is being measured
The primary outcome is the main question the study is designed to answer.
Time to the first severe composite outcome (all-cause hospital admission, ICU admission, or death) within 30 days of treatment assessment.
Measured: 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.
Measured: Participants selected between 01 Dec, 2022 to 31 March 2024
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted3 Dec 2025
- Study start27 Oct 2025
- Primary completion26 Feb 2026
- Study completion26 Feb 2026
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for COVID-19Studies of the same condition, open and under way.
- More trials run by PfizerThe sponsor's other registered studies.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Observational
- Observational model
- Cohort
- Time perspective
- Retrospective
- Enrolment
- 99,000 participants (actual)
Sponsor and investigators
- Lead sponsor
- Pfizer
- Sponsor type
- Industry (pharma, biotech, devices)
- Responsible party
- Sponsor
- Investigators
- Pfizer CT.gov Call Center, Study director, Pfizer
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT07261085
- Sponsor's protocol ID
- C4671071
- Status last verified
- Jun 2026
- First submitted
- 21 Nov 2025
- Last updated
- 29 Jun 2026
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- Yes
- FDA-regulated device
- No
- Individual data sharing
- No: 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.
Study at a glance
From the registry record, last updated by the sponsor on 29 Jun 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- A REAL-WORLD STUDY ON THE EFFECTIVENESS OF NIRMATRELVIR-RITONAVIR IN REDUCING SEVERE OUTCOMES FROM COVID-19
- ClinicalTrials.gov ID
- NCT07261085
- Acronym / sponsor ID
- C4671071
- Conditions
- COVID-19
- Keywords
- Covid-19, SARS-COV2
- Study type
- Observational
- Recruitment status
- Completed
- Enrolment
- 99,000 participants (actual)
- Lead sponsor
- PfizerIndustry (pharma, biotech, devices)
- Study start
- 27 Oct 2025 (actual)
- Primary completion
- 26 Feb 2026 (actual)
- Study completion
- 26 Feb 2026 (actual)
- First posted
- 3 Dec 2025 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
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.
Study design
- Observational model
- Cohort
- Time perspective
- Retrospective
- Number of arms
- 2
| Arm | Type | Receives |
|---|---|---|
| Assessed and Treated Cohort | – | Drug: nirmatrelvir-ritonavirParticipants who were assessed with Covid prescribed and subsequently dispensed nirmatrelvir-ritonavir during the selection period |
| Assessed and Untreated Cohort | – | Other: No treatmentParticipants 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 |
Who may qualify
- Ages
- 18 years and older
- Sex
- All
- Healthy volunteers
- Not accepted
- Age groups
- Adult, Older adult
- 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.
Key inclusion criteria (2 listed)
- 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
Key exclusion criteria (3 listed)
- 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
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| nirmatrelvir-ritonavirAlso: paxlovidParticipants who were assessed with Covid prescribed and subsequently dispensed nirmatrelvir-ritonavir during the selection period | Drug | Assessed and Treated Cohort |
| No treatmentParticipants 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 | Assessed and Untreated Cohort |
Primary outcome
Time to the first severe composite outcome (all-cause hospital admission, ICU admission, or death) within 30 days of treatment assessment.
Time frame: Participants selected between 01 Dec, 2022 to 31 March 2024
1 secondary outcome
Time to the first severe composite outcome (all-cause hospital admission, ICU admission, or death) within 60 days of treatment assessment.
Time frame: Participants selected between 01 Dec, 2022 to 31 March 2024
Results and safety
The study is completed, but results are not available in the source record. That does not mean the treatment did or did not work.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 29 Jun 2026.
- To obtain contact information for a study center near you, click here.Link provided by the sponsor.
- Individual participant dataSharing planned: No. 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.
Related trials for COVID-19
Not yet recruitingPhase 1
Phase I Open-Label Safety Trial of Pembrolizumab for Neurological Post- Acute Sequelae of SARS-CoV-2 (PD1-PASC I)
Post-Acute COVID-19 Syndrome
Active, not recruitingPhase 1
A Safety and Immunogenicity Trial of OCU500, ChAd36 Vector Encoding SARS-CoV-2 Spike Vaccine Via Intranasal and Inhalational Routes in Previously Vaccinated Adults
COVID-19
Active, not recruiting
Intervention to Address Disparate Mental Health Consequences of COVID-19 Pandemic on Latinx and African Newcomers
Mental Health Issue, Mental Health Disorder
Recruiting
Home-Based Exercise Tele-Rehabilitation After COVID-19
Post SARS-CoV2 (COVID-19)
Not yet recruitingPhase 1
A Safety, Reactogenicity and Immunogenicity Trial of RVX-sCPD9 Booster Intranasal COVID-19 Vaccine
COVID -19
Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part. This study is not recruiting at the moment.
Pfizer CT.gov Call Center study director
Pfizer
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
An observational study of COVID-19, run by Pfizer at 1 site in United States.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 2 inclusion and 3 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: finished, as of the sponsor's last update on 29 Jun 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 1 site in United States. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
Are results available for this study?
The study is completed, but results are not available in the source record. That does not mean the treatment did or did not work.
How can a doctor refer a patient or contact the research team?
The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Time to the first severe composite outcome (all-cause hospital admission, ICU admission, or death) within 30 days of treatment assessment. (time frame: Participants selected between 01 Dec, 2022 to 31 March 2024). It is what the study was designed to measure, not a finding.
Where can I read the original study information?
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 29 Jun 2026.