Covid19Phase 4COVAXIDNCT04780659

COVID-19 Vaccination of Immunodeficient Persons (COVAXID)

A Phase 4 study testing Comirnaty (COVID-19, mRNA vaccine) in people with Covid19, run by Karolinska University Hospital at 1 site in Sweden.

Completed

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

Official record

Search all trials

Trial summary

Who is it for?: Ages 18 years and olderHealthy volunteers can take part
Conditions the study is for: Covid19
What is being tested?: Comirnaty (COVID-19, mRNA vaccine)
Type of treatment: Vaccines
Could I receive a placebo?: No, everyone receives an active treatment
How many people: 539 participants
Where: 1 siteSweden
Study dates: 23 Feb 2021to 8 May 2024
Phase: Phase 4
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 18 years and older
All sexes
Healthy volunteers accepted
Adult, Older adult

Who may be able to join

1. Individuals ≥18 years old
2a. In the opinion of the investigator, individuals with immunosuppressive disease who meet one of the following criteria:
Primary immunodeficiency
Human immunodeficiency virus (HIV)-infection
Allogeneic stem cell transplantation / Chimeric antigen receptor (CAR T cell) therapy
Solid organ transplant

Show all 10Show fewer

Chronic lymphatic leukemia
or
2b. In the opinion of the investigator, individuals without immunosuppressive disease or treatment without significant co-morbidity
3. Provision of signed informed consent to participate in the study

Who cannot join

Previous or ongoing Coronavirus Disease-19 (COVID-19).
Coagulation disorders, other conditions associated with prolonged bleeding time or anticoagulant treatments, which according to the investigator contraindicate intramuscular injection. Conditions which can be corrected with measures such as platelet concentrate treatments, coagulation factors or other measures for people responsible for anticoagulants are not exclusion criteria.
Planned to receive another vaccine within 14 days before the first dose of the study vaccine, or during the period from the first dose of the study vaccine up to 14 days after the second dose of the study vaccine, and vaccination with another vaccine which in the investigator's opinion cannot be planned outside these time periods
Pregnancy or breast feeding.
Hypersensitivity to the active substance or to any of the excipients contained in the vaccine
Individuals who cannot understand the informed consent.
Individuals who for other reasons are considered by investigators as not suitable for inclusion

Trial locations and contacts

1 site in 1 country.

Sweden1 site

Karolinska University Hospital
Stockholm, Huddinge, 14186

Other trials in Sweden

About this study

Official title: Immunological Responses After Vaccination for COVID-19 With the Messenger Ribonucleic Acid (mRNA) Vaccine Comirnaty in Immunosuppressed and Immunocompetent Individuals. An Open and Non-randomized, Phase IV Multicenter Study

The study is designed as an open, non-randomized, phase IV cohort study in which the mRNA vaccine Comirnaty will be given in two doses. Analyses will be performed on blood and saliva, investigating humoral and cellular vaccine responses. Occurence of local or systemic reactogenicity will be evaluated, as well as adverse events. The study will include persons with primary or secondary immunosuppressive disorders, as well as immunocompetent persons, with the aim of investigating if the immune responses after given Comirnaty mRNA vaccine against COVID-19.

Read the detailed description

In this study with 450 patients with primary or secondary immunosuppressive disorders (patients with primary immunodeficiency, HIV infected patients, patients with allogenic stem cell transplantation/CAR T cell treated, solid organ transplanted, and patients with chronic lymphatic leukemia) from Karolinska University Hospital, and healthy controls of 90 individuals for comparison, we will investigate the safety and the immune responses after mRNA vaccination with Comirnaty after two doses, under 6 months of time for each participant. The study is In collaboration with research groups at Karolinska Institutet and SciLifeLab, with planned in-depth detailed analyses of antibody responses as well as cellular responses. The study has obtained permission from Swedish Medical Agency and Swedish Ethical Review Authority.

Conditions: Covid19
Being tested: Comirnaty (COVID-19, mRNA vaccine)
Medical subject headings: COVID-19

What participants receive

What participants receive. In a randomised study each person is assigned to one group by chance.

Comirnaty (COVID-19, mRNA vaccine)Biological
Also called tozinameran, Pfizer mRNA vaccine
Comirnaty will be administered two times, one at Day 0 and the second dose at Day 21.

Study groups in NCT04780659
Study group	Role	What they receive
Vaccination with Comirnaty according to standard of care treatment	Experimental	All study participants will receive Comirnaty according to current approval. Receives: Biological: Comirnaty (COVID-19, mRNA vaccine)

What is being measured

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

Assessment of Seroconversion, Defined as Development of Immunoglobulin G (IgG) Antibodies Against Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) After Vaccination of 2 Doses in Seronegative Individuals.
Proportion (95% confidence interval, CI) seroconverting to positive response to SARS-CoV-2 IgG serology test after two doses of vaccine, measured 2 weeks after second dose of vaccine.
Measured: 2 weeks after second dose of vaccine.

Secondary outcomes (5)

Assessment of Any Adverse Events (AE) of the Given Vaccine.
Proportion (95% CI) who experience adverse events, with AE/SAE/SUSAR (after dose 1)
Measured: Duration of 0-14 days after the first vaccine dose.
Assessment of Any Adverse Events (AE) of the Given Vaccine.
Proportion (95% CI) who experience adverse events, with AE/SAE/SUSAR (after dose 2)
Measured: Duration of 0-14 days after the second vaccine dose.
Frequency Who Experience Local and Systemic Reactions
Number and proportion (95% CI) who experience local and systemic reactions (after dose 1)
Measured: After the first vaccin dose
Frequency Who Experience Local and Systemic Reactions
Number and proportion (95% CI) who experience local and systemic reactions (after dose 2)
Measured: After the second vaccin dose
Frequency of SARS-CoV-2 Infection Documented by PCR Test.
Proportion (95% CI) diagnosed with a new SARS-CoV-2 infection confirmed by a positive PCR test
Measured: 0 - 6 months

Timeline

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

23 Feb 20218 May 2024

First posted3 Mar 2021
Study start23 Feb 2021
Primary completion15 Oct 2021
Study completion8 May 2024

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 (5)Papers the sponsor has linked to this study.
Other trials for Covid19Studies of the same condition, open and under way.
More trials run by Karolinska University HospitalThe 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: Interventional
Phase: Phase 4
Primary purpose: Prevention
Allocation: Not applicable
Intervention model: Single group
Masking: None (open label)
Enrolment: 539 participants (actual)

IDs, dates and publications

ClinicalTrials.gov ID: NCT04780659
Sponsor's protocol ID: 2021-000175-37
Acronym: COVAXID
Status last verified: Nov 2025
First submitted: 19 Feb 2021
Last updated: 4 Dec 2025
Results posted: Yes, on ClinicalTrials.gov
Data monitoring committee: No
FDA-regulated drug: No
FDA-regulated device: No
Individual data sharing: Yes: Will submit data to European Union Drug Regulating Authorities Clinical Trials Database (EudraCT) and share data result. Will share research results and data through national COVID-19 data portal, operated by SciLifeLab Data Centre, Sweden.

Publications

Chen P, Bergman P, Blennow O, Hansson L, Mielke S, Nowak P, Gao Y, Soderdahl G, Osterborg A, Smith CIE, Vesterbacka J, Wullimann D, Cuapio A, Akber M, Bogdanovic G, Muschiol S, Aberg M, Lore K, Chen MS, Ljungman P, Buggert M, Aleman S, Ljunggren HG. Real-world assessment of immunogenicity in immunocompromised individuals following SARS-CoV-2 mRNA vaccination: a two-year follow-up of the prospective clinical trial COVAXID. EBioMedicine. 2024 Nov;109:105385. doi: 10.1016/j.ebiom.2024.105385. Epub 2024 Oct 11.
PubMed 39395230
Muller TR, Gao Y, Wu J, Ribeiro O, Chen P, Bergman P, Blennow O, Hansson L, Mielke S, Nowak P, Vesterbacka J, Akber M, Soderdahl G, Smith CIE, Lore K, Chen MS, Ljungman P, Ingelman-Sundberg HM, Ljunggren HG, Osterborg A, Sette A, Grifoni A, Aleman S, Buggert M. Memory T cells effectively recognize the SARS-CoV-2 hypermutated BA.2.86 variant. Cell Host Microbe. 2024 Feb 14;32(2):156-161.e3. doi: 10.1016/j.chom.2023.12.010. Epub 2024 Jan 10.
PubMed 38211584
Chen P, Bergman P, Blennow O, Hansson L, Mielke S, Nowak P, Soderdahl G, Osterborg A, Smith CIE, Vesterbacka J, Wullimann D, Cuapio A, Akber M, Bogdanovic G, Muschiol S, Aberg M, Lore K, Sallberg Chen M, Buggert M, Ljungman P, Aleman S, Ljunggren HG. Real-world assessment of immunogenicity in immunocompromised individuals following SARS-CoV-2 mRNA vaccination: a one-year follow-up of the prospective clinical trial COVAXID. EBioMedicine. 2023 Aug;94:104700. doi: 10.1016/j.ebiom.2023.104700. Epub 2023 Jul 13.
PubMed 37453361
Cuapio A, Boulouis C, Filipovic I, Wullimann D, Kammann T, Parrot T, Chen P, Akber M, Gao Y, Hammer Q, Strunz B, Perez Potti A, Rivera Ballesteros O, Lange J, Muvva JR, Bergman P, Blennow O, Hansson L, Mielke S, Nowak P, Soderdahl G, Osterborg A, Smith CIE, Bogdanovic G, Muschiol S, Hellgren F, Lore K, Sobkowiak MJ, Gabarrini G, Healy K, Sallberg Chen M, Alici E, Bjorkstrom NK, Buggert M, Ljungman P, Sandberg JK, Aleman S, Ljunggren HG. NK cell frequencies, function and correlates to vaccine outcome in BNT162b2 mRNA anti-SARS-CoV-2 vaccinated healthy and immunocompromised individuals. Mol Med. 2022 Feb 8;28(1):20. doi: 10.1186/s10020-022-00443-2.
PubMed 35135470
Healy K, Pin E, Chen P, Soderdahl G, Nowak P, Mielke S, Hansson L, Bergman P, Smith CIE, Ljungman P, Valentini D, Blennow O, Osterborg A, Gabarrini G, Al-Manei K, Alkharaan H, Sobkowiak MJ, Yousef J, Mravinacova S, Cuapio A, Xu X, Akber M, Lore K, Hellstrom C, Muschiol S, Bogdanovic G, Buggert M, Ljunggren HG, Hober S, Nilsson P, Aleman S, Sallberg Chen M. Salivary IgG to SARS-CoV-2 indicates seroconversion and correlates to serum neutralization in mRNA-vaccinated immunocompromised individuals. Med. 2022 Feb 11;3(2):137-153.e3. doi: 10.1016/j.medj.2022.01.001. Epub 2022 Jan 20.
PubMed 35075450

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 Covid19 trials

Study at a glance

From the registry record, last updated by the sponsor on 4 Dec 2025. Recruitment status is as the sponsor reported it: confirm with the study team.

Official title: Immunological Responses After Vaccination for COVID-19 With the Messenger Ribonucleic Acid (mRNA) Vaccine Comirnaty in Immunosuppressed and Immunocompetent Individuals. An Open and Non-randomized, Phase IV Multicenter Study
ClinicalTrials.gov ID: NCT04780659
Acronym / sponsor ID: COVAXID / 2021-000175-37
Conditions: Covid19
Phase: Phase 4
Study type: Interventional
Recruitment status: Completed
Enrolment: 539 participants (actual)
Lead sponsor: Karolinska University HospitalUniversity, hospital or other
Collaborators: Karolinska Institutet
Study start: 23 Feb 2021 (actual)
Primary completion: 15 Oct 2021 (actual)
Study completion: 8 May 2024 (actual)
First posted: 3 Mar 2021 (actual)
Results: Posted 4 Dec 2025

Clinical summary

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

Detailed description

Study design

Primary purpose: Prevention
Allocation: Not applicable
Intervention model: Single group
Masking: None (open label)
Number of arms: 1

Arm	Type	Receives
Vaccination with Comirnaty according to standard of care treatment	Experimental	Biological: Comirnaty (COVID-19, mRNA vaccine)All study participants will receive Comirnaty according to current approval.

Who may qualify

Ages: 18 years and older
Sex: All
Healthy volunteers: Accepted
Age groups: Adult, Older adult

Key inclusion criteria (10 listed)

1. Individuals ≥18 years old
2a. In the opinion of the investigator, individuals with immunosuppressive disease who meet one of the following criteria:
Primary immunodeficiency
Human immunodeficiency virus (HIV)-infection
Allogeneic stem cell transplantation / Chimeric antigen receptor (CAR T cell) therapy

Key exclusion criteria (7 listed)

Previous or ongoing Coronavirus Disease-19 (COVID-19).
Coagulation disorders, other conditions associated with prolonged bleeding time or anticoagulant treatments, which according to the investigator contraindicate intramuscular injection. Conditions which can be corrected with measures such as platelet concentrate treatments, coagulation factors or other measures for people responsible for anticoagulants are not exclusion criteria.
Planned to receive another vaccine within 14 days before the first dose of the study vaccine, or during the period from the first dose of the study vaccine up to 14 days after the second dose of the study vaccine, and vaccination with another vaccine which in the investigator's opinion cannot be planned outside these time periods
Pregnancy or breast feeding.
Hypersensitivity to the active substance or to any of the excipients contained in the vaccine

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
Comirnaty (COVID-19, mRNA vaccine)Also: tozinameran, Pfizer mRNA vaccineComirnaty will be administered two times, one at Day 0 and the second dose at Day 21.	Biological	Vaccination with Comirnaty according to standard of care treatment

Primary outcome

Assessment of Seroconversion, Defined as Development of Immunoglobulin G (IgG) Antibodies Against Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) After Vaccination of 2 Doses in Seronegative Individuals.
Time frame: 2 weeks after second dose of vaccine.
Proportion (95% confidence interval, CI) seroconverting to positive response to SARS-CoV-2 IgG serology test after two doses of vaccine, measured 2 weeks after second dose of vaccine.

5 secondary outcomes

Assessment of Any Adverse Events (AE) of the Given Vaccine.
Time frame: Duration of 0-14 days after the first vaccine dose.
Assessment of Any Adverse Events (AE) of the Given Vaccine.
Time frame: Duration of 0-14 days after the second vaccine dose.
Frequency Who Experience Local and Systemic Reactions
Time frame: After the first vaccin dose
Frequency Who Experience Local and Systemic Reactions
Time frame: After the second vaccin dose
Frequency of SARS-CoV-2 Infection Documented by PCR Test.
Time frame: 0 - 6 months

Results and safety

Results posted to the registry on 4 Dec 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
All Immunocompromised Patients	449	439
Controls	90	90

Primary outcome: Assessment of Seroconversion, Defined as Development of Immunoglobulin G (IgG) Antibodies Against Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) After Vaccination of 2 Doses in Seronegative Individuals.

Time frame: 2 weeks after second dose of vaccine.. Count of participants. Unit: Participants

Measure	All Immunocompromised Patients n = 388	Controls n = 78
Seroconverted	280	78
Seronegative	108	0

All Immunocompromised Patients vs Controls: p < 0.05, Fisher Exact

5 secondary outcomes are reported in the full results.

Adverse events

Time frame: Adverse events (AEs) were recorded from the time of inclusion until visit 4, which occurred two weeks after administration of the second vaccine dose. Serious Adverse events (SAE) were documented up to visit 5, six weeks after the second vaccine dose.. Other adverse events reported at 0% frequency or more

Group	Serious adverse events	Other adverse events	Deaths
All Immunocompromised Patients	23 of 449 (5.1%)	173 of 449 (38.5%)	5 of 449
Controls	0 of 90 (0%)	11 of 90 (12.2%)	0 of 90

Loading the posted results from ClinicalTrials.gov…

Research links

Official record on ClinicalTrials.govLast updated by the sponsor 4 Dec 2025.
Posted resultsParticipant flow, baseline, all outcome measures and adverse events.
Derived from this study: PubMed 39395230Chen P, Bergman P, Blennow O, Hansson L, Mielke S, Nowak P, Gao Y, Soderdahl G, Osterborg A, Smith CIE, Vesterbacka J, Wullimann D, Cuapio A, Akber M, Bogdanovic G, Muschiol S, Aberg M, Lore K, Chen MS, Ljungman P, Buggert M, Aleman S, Ljunggren HG. Real-world assessment of immunogenicity in immunocompromised individuals following SARS-CoV-2 mRNA vaccination: a two-year follow-up of the prospective clinical trial COVAXID. EBioMedicine. 2024 Nov;109:105385. doi: 10.1016/j.ebiom.2024.105385. Epub 2024 Oct 11.
Derived from this study: PubMed 38211584Muller TR, Gao Y, Wu J, Ribeiro O, Chen P, Bergman P, Blennow O, Hansson L, Mielke S, Nowak P, Vesterbacka J, Akber M, Soderdahl G, Smith CIE, Lore K, Chen MS, Ljungman P, Ingelman-Sundberg HM, Ljunggren HG, Osterborg A, Sette A, Grifoni A, Aleman S, Buggert M. Memory T cells effectively recognize the SARS-CoV-2 hypermutated BA.2.86 variant. Cell Host Microbe. 2024 Feb 14;32(2):156-161.e3. doi: 10.1016/j.chom.2023.12.010. Epub 2024 Jan 10.
Derived from this study: PubMed 37453361Chen P, Bergman P, Blennow O, Hansson L, Mielke S, Nowak P, Soderdahl G, Osterborg A, Smith CIE, Vesterbacka J, Wullimann D, Cuapio A, Akber M, Bogdanovic G, Muschiol S, Aberg M, Lore K, Sallberg Chen M, Buggert M, Ljungman P, Aleman S, Ljunggren HG. Real-world assessment of immunogenicity in immunocompromised individuals following SARS-CoV-2 mRNA vaccination: a one-year follow-up of the prospective clinical trial COVAXID. EBioMedicine. 2023 Aug;94:104700. doi: 10.1016/j.ebiom.2023.104700. Epub 2023 Jul 13.
Derived from this study: PubMed 35135470Cuapio A, Boulouis C, Filipovic I, Wullimann D, Kammann T, Parrot T, Chen P, Akber M, Gao Y, Hammer Q, Strunz B, Perez Potti A, Rivera Ballesteros O, Lange J, Muvva JR, Bergman P, Blennow O, Hansson L, Mielke S, Nowak P, Soderdahl G, Osterborg A, Smith CIE, Bogdanovic G, Muschiol S, Hellgren F, Lore K, Sobkowiak MJ, Gabarrini G, Healy K, Sallberg Chen M, Alici E, Bjorkstrom NK, Buggert M, Ljungman P, Sandberg JK, Aleman S, Ljunggren HG. NK cell frequencies, function and correlates to vaccine outcome in BNT162b2 mRNA anti-SARS-CoV-2 vaccinated healthy and immunocompromised individuals. Mol Med. 2022 Feb 8;28(1):20. doi: 10.1186/s10020-022-00443-2.
Derived from this study: PubMed 35075450Healy K, Pin E, Chen P, Soderdahl G, Nowak P, Mielke S, Hansson L, Bergman P, Smith CIE, Ljungman P, Valentini D, Blennow O, Osterborg A, Gabarrini G, Al-Manei K, Alkharaan H, Sobkowiak MJ, Yousef J, Mravinacova S, Cuapio A, Xu X, Akber M, Lore K, Hellstrom C, Muschiol S, Bogdanovic G, Buggert M, Ljunggren HG, Hober S, Nilsson P, Aleman S, Sallberg Chen M. Salivary IgG to SARS-CoV-2 indicates seroconversion and correlates to serum neutralization in mRNA-vaccinated immunocompromised individuals. Med. 2022 Feb 11;3(2):137-153.e3. doi: 10.1016/j.medj.2022.01.001. Epub 2022 Jan 20.
Individual participant dataSharing planned: Yes. Will submit data to European Union Drug Regulating Authorities Clinical Trials Database (EudraCT) and share data result. Will share research results and data through national COVID-19 data portal, operated by SciLifeLab Data Centre, Sweden.

Related trials for Covid19

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.

Soo Aleman, MD, PhD principal investigator

Karolinska University Hospital, ME Infectious Diseases

1 site in 1 country: see every site and its status.

Questions about this trial

What is this clinical trial studying?

A Phase 4 study testing Comirnaty (COVID-19, mRNA vaccine) in people with Covid19, run by Karolinska University Hospital at 1 site in Sweden.

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 10 inclusion and 7 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 4 Dec 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 Sweden. 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.

What does this phase mean?

Phase 4 studies take place after a treatment is approved, to learn more about its long-term benefits and risks in everyday use.

Not every study follows the same path, and some studies (observational studies, device studies) have no phase.

Are results available for this study?

Yes. Results are posted in the registry (first posted 4 Dec 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?

Assessment of Seroconversion, Defined as Development of Immunoglobulin G (IgG) Antibodies Against Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) After Vaccination of 2 Doses in Seronegative Individuals. (time frame: 2 weeks after second dose of vaccine.). 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 NCT04780659, which also lists 5 linked publications.

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 4 Dec 2025.