SARS-CoV-2 InfectionNCT05263908

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

An observational study of SARS-CoV-2 Infection, run by Pfizer at 1 site in Japan.

Completed

Finished. The study has ended and is not enrolling. Results may be posted on the official record.

Trial summary

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. Read more about this study

Who is it for?: Ages 12 years and older
Conditions the study is for: SARS-CoV-2 Infection
What is being tested?: nirmatrelvir / ritonavir
Type of treatment: Pill or oral medicine
How many people: 3,346 participants
Where: 1 siteJapan
Study dates: 31 Mar 2022to 10 Jul 2023
Phase: Observational
Are there results?: Yes, posted in the registrySummary in the doctors' view

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 12 years and older
All sexes
No healthy volunteers
Child, Adult, Older adult

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

Who may be able to join

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

Who cannot join

There are no exclusion criteria for this study.

Trial locations and contacts

1 site in 1 country.

Japan1 site

Pfizer Local County
Tokyo, 1518589

Other trials in Japan

About this study

Official title: General Investigation for PAXLOVID PAC

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.

Read the 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.

Conditions: SARS-CoV-2 Infection
Being tested: nirmatrelvir / ritonavir
Keywords: severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), coronavirus disease 2019 (COVID-19), Paxlovid, Nirmatrelvir
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 PACK
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.

Study groups in NCT05263908
Study group	Role	What they receive
PAXLOVID PACK		Subjects administered PAXLOVID PACK Receives: Drug: nirmatrelvir / ritonavir

What is being measured

The primary outcome is the main question the study is designed to answer.

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.
Measured: From the start date of treatment with Paxlovid PACK to 28 days after the end of treatment, up to approximately 45 days.

Secondary outcomes (5)

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."
Measured: 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."
Measured: 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."
Measured: 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.
Measured: 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.
Measured: 3, 5, 7, 14, 21 and 28 days after the start of administration with Paxlovid PACK.

Timeline

From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.

31 Mar 202210 Jul 2023

First posted3 Mar 2022
Study start31 Mar 2022
Primary completion10 Jul 2023
Study completion10 Jul 2023

Resources

Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
Posted resultsParticipant flow, outcome measures and adverse events reported by the sponsor.
Publications (1)Papers the sponsor has linked to this study.
Other trials for SARS-CoV-2 InfectionStudies 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: Case only
Time perspective: Prospective
Enrolment: 3,346 participants (actual)

IDs, dates and publications

ClinicalTrials.gov ID: NCT05263908
Sponsor's protocol ID: C4671018
Other IDs: NCT05263908
Status last verified: Aug 2025
First submitted: 25 Feb 2022
Last updated: 3 Sep 2025
Results posted: Yes, on ClinicalTrials.gov
Data monitoring committee: 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.

Publications

Murata K, Hyokai S, Fujii Y, Morimasa M. Real-world safety of nirmatrelvir plus ritonavir in patients with COVID-19 in Japan: A post-marketing surveillance study. Jpn J Infect Dis. 2026 Jan 30. doi: 10.7883/yoken.JJID.2024.380. Online ahead of print.
PubMed 41621946

Want to know more?

The sponsor has not listed a contact. The official record may have more details.

Talk to your doctor first and take this page with you. Only the study team can confirm whether you can join.

Questions to ask the study team

What is the study trying to find out?
What would I need to do, and how often would I visit?
Could I receive a placebo instead of the treatment?
What are the possible risks and benefits for me?
Will it cost me anything? Are travel or time paid for?
Can I keep seeing my own doctor during the study?
What happens when the study ends?

See locations

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

All SARS-CoV-2 Infection trials

Study at a glance

From the registry record, last updated by the sponsor on 3 Sep 2025. Recruitment status is as the sponsor reported it: confirm with the study team.

Official title: General Investigation for PAXLOVID PAC
ClinicalTrials.gov ID: NCT05263908
Acronym / sponsor ID: C4671018
Conditions: SARS-CoV-2 Infection
Keywords: severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), coronavirus disease 2019 (COVID-19), Paxlovid, Nirmatrelvir
Study type: Observational
Recruitment status: Completed
Enrolment: 3,346 participants (actual)
Lead sponsor: PfizerIndustry (pharma, biotech, devices)
Study start: 31 Mar 2022 (actual)
Primary completion: 10 Jul 2023 (actual)
Study completion: 10 Jul 2023 (actual)
First posted: 3 Mar 2022 (actual)
Results: Posted 3 Sep 2025

Clinical summary

The research question as the sponsor registered it. This describes what the study plans to test, not what it found.

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.

Detailed description

Study design

Observational model: Case only
Time perspective: Prospective
Number of arms: 1

Arm	Type	Receives
PAXLOVID PACK	–	Drug: nirmatrelvir / ritonavirSubjects administered PAXLOVID PACK

Who may qualify

Ages: 12 years and older
Sex: All
Healthy volunteers: Not accepted
Age groups: Child, Adult, Older adult
Study population: The subjects who have been treated with PAXLOVID PACK for the first time.

Key inclusion criteria (1 listed)

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

Key exclusion criteria (1 listed)

There are no exclusion criteria for this study.

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: PAXLOVID PACKThe 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.	Drug	PAXLOVID PACK

Primary outcome

Incidence of Adverse Drug Reactions
Time frame: From the start date of treatment with Paxlovid PACK to 28 days after the end of treatment, up to approximately 45 days.
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.

5 secondary outcomes

Percentage of Participants With Worsening Severity (Efficacy Analysis Set #1)
Time frame: 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)
Time frame: 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)
Time frame: 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)
Time frame: 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)
Time frame: 3, 5, 7, 14, 21 and 28 days after the start of administration with Paxlovid PACK.

Results and safety

Results posted to the registry on 3 Sep 2025, as reported by the sponsor. Figures are copied from the record, not re-analysed. Full results on ClinicalTrials.gov.

Participant flow

Group	Started	Completed
Paxlovid PACK (Nirmatrelvir/Ritonavir)	3,346	2,948

Primary outcome: Incidence of Adverse Drug Reactions

Time frame: From the start date of treatment with Paxlovid PACK to 28 days after the end of treatment, up to approximately 45 days.. Count of participants. Unit: Participants

Measure	Paxlovid PACK (Nirmatrelvir/Ritonavir) n = 2829
ADR	423
SADR	6

Population analysed: The safety analysis set (2829 participants) comprised of participants who satisfied the inclusion criteria. Participants with no informed consent for publication of study results, no information on administration, and no information on adverse events - no re-visits were excluded.

5 secondary outcomes are reported in the full results.

Adverse events

Time frame: From the start date of treatment with Paxlovid PACK to 28 days after the end of treatment, up to approximately 45days.. Other adverse events reported at 0.1% frequency or more

Group	Serious adverse events	Other adverse events	Deaths
Paxlovid PACK (Nirmatrelvir/Ritonavir)	51 of 2,829 (1.8%)	474 of 2,829 (16.8%)	16 of 2,829

Loading the posted results from ClinicalTrials.gov…

Research links

Official record on ClinicalTrials.govLast updated by the sponsor 3 Sep 2025.
Posted resultsParticipant flow, baseline, all outcome measures and adverse events.
Derived from this study: PubMed 41621946Murata K, Hyokai S, Fujii Y, Morimasa M. Real-world safety of nirmatrelvir plus ritonavir in patients with COVID-19 in Japan: A post-marketing surveillance study. Jpn J Infect Dis. 2026 Jan 30. doi: 10.7883/yoken.JJID.2024.380. Online ahead of print.
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 SARS-CoV-2 Infection

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 SARS-CoV-2 Infection, run by Pfizer at 1 site in Japan.

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 1 inclusion and 1 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 3 Sep 2025. 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 Japan. 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?

Yes. Results are posted in the registry (first posted 3 Sep 2025). A summary is in the For doctors view, and the full results are on ClinicalTrials.gov.

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?

Incidence of Adverse Drug Reactions (time frame: From the start date of treatment with Paxlovid PACK to 28 days after the end of treatment, up to approximately 45 days.). It is what the study was designed to measure, not a finding.

Where can I read the original study information?

On the ClinicalTrials.gov record for NCT05263908, which also lists 1 linked publication.

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 3 Sep 2025.