COVID 19 VaccinePhase 4NCT05057182
Third Dose of mRNA Vaccination to Boost COVID-19 Immunity (mBoost Study)
A Phase 4 study testing BNT162b2 in people with COVID 19 Vaccine, run by The University of Hong Kong at 1 site in Hong Kong.
Trial summary
300 adults ≥30 years of age who have previously received two doses of an inactivated COVID-19 vaccine at least 3 months earlier will receive a third dose with an mRNA vaccine (BNT162b2, BioNTech). Investigators will monitor reactogenicity and measure the immune response to the third dose. Read more about this study
- Who is it for?
- Ages 30 years and olderHealthy volunteers can take part
- Conditions the study is for
- COVID 19 Vaccine
- What is being tested?
- BNT162b2
- Type of treatment
- Vaccines
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 300 participants
- Where
- 1 siteHong Kong
- Study dates
- 18 Oct 2021to 31 Dec 2024
- Phase
- Phase 4
- 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 30 years and older
- All sexes
- Healthy volunteers accepted
- Adult, Older adult
Who may be able to join
- Aged 30 years or older at enrolment.
- Have received two doses of any inactivated COVID-19 vaccines (for example Sinovac- CoronaVac, Sinopharm-BIBP) with the most recent dose at least 90 days prior to enrolment.
- Currently resident and planning to remain resident in Hong Kong during the duration of the study, i.e. for 12 months after enrolment.
- Agreement to refrain from blood donation during the course of the study.
- Willing to provide blood samples for all the required time points.
- The individual or their caregiver have a home phone or cellular or mobile phone for communications purpose.
- Capable of providing informed consent.
Who cannot join
- A history of laboratory-confirmed or clinically confirmed COVID-19 infection. Have received (at least one dose of) any COVID-19 vaccines other than inactivated vaccines.
- Individuals who report any medical condition, or as determined by a clinician, not suitable to receive mRNA vaccines, including but not limited to allergies to the active substance or other ingredients of the vaccine.
- With diagnosed medical conditions related to their immune system.
- Use of medication that impairs immune system in the last 6 months, except topical steroids or short-term oral steroids (course lasting ≤ 14 days).
- Have used immunoglobulins and/or any blood products within 90 days prior to enrolment (administration of the study vaccine).
- Pregnancy, lactation or intention to become pregnant in the coming 3 months.
Trial locations and contacts
1 site in 1 country.
About this study
Official title: mRNA Vaccination to Boost Antibodies Against SARS-CoV-2 in Recipients of Inactivated Vaccines (the "mBoost" Study)
300 adults ≥30 years of age who have previously received two doses of an inactivated COVID-19 vaccine at least 3 months earlier will receive a third dose with an mRNA vaccine (BNT162b2, BioNTech). Investigators will monitor reactogenicity and measure the immune response to the third dose.
Read the detailed description
Background: The accrual of population immunity to COVID-19 could allow life to return to pre- pandemic normality. Immunity can be acquired through natural infections or, preferably, by vaccination. An unprecedented global effort has succeeded in developing a number of COVID-19 vaccines. All vaccines against COVID-19 approved until now have originally been developed as either a single dose or following a homologous two-dose regimen. Inactivated COVID-19 vaccines have shown inferior immunogenicity compared to mRNA vaccines but there are no studies looking into the immunogenicity, reactogenicity and safety profile of mRNA vaccination provided as a booster dose in individuals who have previously received two doses of an inactivated COVID-19 vaccine.
Aims and Objectives: The aims of this study are: (1) to determine whether one dose of mRNA vaccine can boost neutralizing antibodies against SARS-CoV-2 in individuals who have previously received two doses of inactivated COVID-19 vaccines, and (2) to assess the reactogenicity and safety of heterologous 3rd doses of vaccination. The specific primary objective of this study is to assess the vaccine (humoral) immunogenicity, proxy by SARS-CoV-2 serum neutralizing antibody titers, of a 3rd dose dose of mRNA vaccine (using BNT162b2, Fosun/BioNTech) at 28 days after the booster dose in individuals who have previously received two doses of any inactivated COVID-19 vaccines.
Study design: Open label trial in adults aged 30 years of age or older (at enrolment). The duration of participation for each participant will be 12 months from the administration of the 3rd vaccine dose. The immune response and reactogenicity of one dose of BNT162b2 will be investigated in individuals who previously received two doses of any inactivated COVID-19 vaccines at least 3 months earlier. Participants will be enrolled shortly before receiving the booster dose of BNT162b2 (day 0), with blood collection at days 0, 28, 182 and 365 days after enrolment for analysis of humoral immune responses.
Main outcomes: The primary outcome is the vaccine immunogenicity measured as SARS-CoV-2 serum neutralizing antibodies in individuals who previously received two doses of any inactivated COVID-19 vaccines, evaluated as the geometric mean titer (GMT) at 28 days after the 3rd dose. The secondary outcomes include (1) a comparison of SARS- CoV-2 serum neutralizing antibodies as the geometric mean fold rise from baseline to each post-vaccination timepoint (i.e. at days 28, 182 and 365), and (2) descriptive analysis of the reactogenicity and safety profile of the 3rd dose.
Target population: Adults aged 30 years or older
Number of Subjects Planned: 300 participants to be recruited between September 2021 and December 2021
Study duration: 12 months for each participant
Potential implications: This study will provide important evidence into the effects of using a 3rd dose of mRNA vaccines to boost the immune response in individuals that had previously received two doses of inactivated vaccines. This information together with data collected on reactogenicity and safety could inform COVID-19 vaccination policy locally and internationally.
- Conditions
- COVID 19 Vaccine
- Being tested
- BNT162b2
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
BNT162b2Biological
Also called Comirnaty
BNT162b2 mRNA vaccine (Cominarty®, BioNTech/Fosun Pharma), one dose (0.3mL after dilution) contains 30 micrograms of COVID-19 mRNA Vaccine embedded in lipid nanoparticles.
| Study group | Role | What they receive |
|---|---|---|
| BNT162b2 | Experimental | BNT162b2 mRNA vaccine (Cominarty®, BioNTech/Fosun Pharma), one dose (0.3mL after dilution) contains 30 micrograms of COVID-19 mRNA Vaccine embedded in lipid nanoparticles. Receives: Biological: BNT162b2 |
What is being measured
The primary outcome is the main question the study is designed to answer.
Geometric Mean Titer of SARS-CoV-2 serum neutralizing antibodies
The primary outcome measure is the vaccine (humoral) immunogenicity at 28 days after the booster dose of BNT162b2 in individuals who have previously received two doses of any inactivated COVID-19 vaccines, measured as geometric mean titer (GMT) of SARS-CoV-2 serum neutralizing antibodies using plaque reduction neutralization test (PRNT).
Measured: 28 days after vaccination
Secondary outcomes (4)
Geometric Mean Titer of SARS-CoV-2 serum neutralizing antibodies
Measured: 182 and 365 days after vaccination
The geometric mean fold rise (GMFR) of SARS-CoV-2 serum neutralizing antibody titers from baseline to each post-vaccination timepoint measured.
Measured: Day 28, 49, 182 and 365 after vaccination
Reactogenicity
Incidence of solicited local and systemic adverse events after the booster dose of vaccination.
Measured: 7 days after vaccination or until the last symptom disappears
Hospitalizations from any cause
Incidence of hospitalizations during the year after receipt of the booster dose.
Measured: 365 days after vaccination
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted27 Sep 2021
- Study start18 Oct 2021
- Primary completion31 Mar 2024
- Study completion31 Dec 2024
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Publications (2)Papers the sponsor has linked to this study.
- Other trials for COVID 19 VaccineStudies of the same condition, open and under way.
- More trials run by The University of Hong KongThe 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
- 300 participants (actual)
Sponsor and investigators
- Lead sponsor
- The University of Hong Kong
- Sponsor type
- University, hospital or other
- Responsible party
- Sponsor
- Investigators
- Benjamin J Cowling, PhD, Principal investigator, The University of Hong Kong
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT05057182
- Sponsor's protocol ID
- BJC050
- Status last verified
- Apr 2026
- First submitted
- 24 Sep 2021
- Last updated
- 15 May 2026
- Results posted
- No
- Data monitoring committee
- Yes
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- Yes
Publications
Shiu EYC, Cheng SMS, Martin-Sanchez M, Au NYM, Chan KCK, Li JKC, Fung LWC, Luk LLH, Chaothai S, Kwan TC, Ip DKM, Leung GM, Poon LLM, Peiris JSM, Leung NHL, Cowling BJ. Durability for 12 months of antibody response to a booster dose of monovalent BNT162b2 in adults who had initially received 2 doses of inactivated vaccine. Vaccine. 2024 Dec 2;42(26):126317. doi: 10.1016/j.vaccine.2024.126317. Epub 2024 Sep 13.
PubMed 39276621Leung NHL, Cheng SMS, Martin-Sanchez M, Au NYM, Ng YY, Luk LLH, Chan KCK, Li JKC, Leung YWY, Tsang LCH, Chaothai S, Kwan KKH, Ip DKM, Poon LLM, Leung GM, Peiris JSM, Cowling BJ. Immunogenicity of a Third Dose of BNT162b2 to Ancestral Severe Acute Respiratory Syndrome Coronavirus 2 and the Omicron Variant in Adults Who Received 2 Doses of Inactivated Vaccine. Clin Infect Dis. 2023 Feb 8;76(3):e299-e307. doi: 10.1093/cid/ciac458.
PubMed 35675370
Study at a glance
From the registry record, last updated by the sponsor on 15 May 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- mRNA Vaccination to Boost Antibodies Against SARS-CoV-2 in Recipients of Inactivated Vaccines (the "mBoost" Study)
- ClinicalTrials.gov ID
- NCT05057182
- Acronym / sponsor ID
- BJC050
- Conditions
- COVID 19 Vaccine
- Phase
- Phase 4
- Study type
- Interventional
- Recruitment status
- Completed
- Enrolment
- 300 participants (actual)
- Lead sponsor
- The University of Hong KongUniversity, hospital or other
- Study start
- 18 Oct 2021 (actual)
- Primary completion
- 31 Mar 2024 (actual)
- Study completion
- 31 Dec 2024 (actual)
- First posted
- 27 Sep 2021 (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.
300 adults ≥30 years of age who have previously received two doses of an inactivated COVID-19 vaccine at least 3 months earlier will receive a third dose with an mRNA vaccine (BNT162b2, BioNTech). Investigators will monitor reactogenicity and measure the immune response to the third dose.
Detailed description
Background: The accrual of population immunity to COVID-19 could allow life to return to pre- pandemic normality. Immunity can be acquired through natural infections or, preferably, by vaccination. An unprecedented global effort has succeeded in developing a number of COVID-19 vaccines. All vaccines against COVID-19 approved until now have originally been developed as either a single dose or following a homologous two-dose regimen. Inactivated COVID-19 vaccines have shown inferior immunogenicity compared to mRNA vaccines but there are no studies looking into the immunogenicity, reactogenicity and safety profile of mRNA vaccination provided as a booster dose in individuals who have previously received two doses of an inactivated COVID-19 vaccine.
Aims and Objectives: The aims of this study are: (1) to determine whether one dose of mRNA vaccine can boost neutralizing antibodies against SARS-CoV-2 in individuals who have previously received two doses of inactivated COVID-19 vaccines, and (2) to assess the reactogenicity and safety of heterologous 3rd doses of vaccination. The specific primary objective of this study is to assess the vaccine (humoral) immunogenicity, proxy by SARS-CoV-2 serum neutralizing antibody titers, of a 3rd dose dose of mRNA vaccine (using BNT162b2, Fosun/BioNTech) at 28 days after the booster dose in individuals who have previously received two doses of any inactivated COVID-19 vaccines.
Study design: Open label trial in adults aged 30 years of age or older (at enrolment). The duration of participation for each participant will be 12 months from the administration of the 3rd vaccine dose. The immune response and reactogenicity of one dose of BNT162b2 will be investigated in individuals who previously received two doses of any inactivated COVID-19 vaccines at least 3 months earlier. Participants will be enrolled shortly before receiving the booster dose of BNT162b2 (day 0), with blood collection at days 0, 28, 182 and 365 days after enrolment for analysis of humoral immune responses.
Main outcomes: The primary outcome is the vaccine immunogenicity measured as SARS-CoV-2 serum neutralizing antibodies in individuals who previously received two doses of any inactivated COVID-19 vaccines, evaluated as the geometric mean titer (GMT) at 28 days after the 3rd dose. The secondary outcomes include (1) a comparison of SARS- CoV-2 serum neutralizing antibodies as the geometric mean fold rise from baseline to each post-vaccination timepoint (i.e. at days 28, 182 and 365), and (2) descriptive analysis of the reactogenicity and safety profile of the 3rd dose.
Target population: Adults aged 30 years or older
Number of Subjects Planned: 300 participants to be recruited between September 2021 and December 2021
Study duration: 12 months for each participant
Potential implications: This study will provide important evidence into the effects of using a 3rd dose of mRNA vaccines to boost the immune response in individuals that had previously received two doses of inactivated vaccines. This information together with data collected on reactogenicity and safety could inform COVID-19 vaccination policy locally and internationally.
Study design
- Primary purpose
- Prevention
- Allocation
- Not applicable
- Intervention model
- Single group
- Masking
- None (open label)
- Number of arms
- 1
| Arm | Type | Receives |
|---|---|---|
| BNT162b2 | Experimental | Biological: BNT162b2BNT162b2 mRNA vaccine (Cominarty®, BioNTech/Fosun Pharma), one dose (0.3mL after dilution) contains 30 micrograms of COVID-19 mRNA Vaccine embedded in lipid nanoparticles. |
Who may qualify
- Ages
- 30 years and older
- Sex
- All
- Healthy volunteers
- Accepted
- Age groups
- Adult, Older adult
Key inclusion criteria (7 listed)
- Aged 30 years or older at enrolment.
- Have received two doses of any inactivated COVID-19 vaccines (for example Sinovac- CoronaVac, Sinopharm-BIBP) with the most recent dose at least 90 days prior to enrolment.
- Currently resident and planning to remain resident in Hong Kong during the duration of the study, i.e. for 12 months after enrolment.
- Agreement to refrain from blood donation during the course of the study.
- Willing to provide blood samples for all the required time points.
Key exclusion criteria (6 listed)
- A history of laboratory-confirmed or clinically confirmed COVID-19 infection. Have received (at least one dose of) any COVID-19 vaccines other than inactivated vaccines.
- Individuals who report any medical condition, or as determined by a clinician, not suitable to receive mRNA vaccines, including but not limited to allergies to the active substance or other ingredients of the vaccine.
- With diagnosed medical conditions related to their immune system.
- Use of medication that impairs immune system in the last 6 months, except topical steroids or short-term oral steroids (course lasting ≤ 14 days).
- Have used immunoglobulins and/or any blood products within 90 days prior to enrolment (administration of the study 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 |
|---|---|---|
| BNT162b2Also: ComirnatyBNT162b2 mRNA vaccine (Cominarty®, BioNTech/Fosun Pharma), one dose (0.3mL after dilution) contains 30 micrograms of COVID-19 mRNA Vaccine embedded in lipid nanoparticles. | Biological | BNT162b2 |
Primary outcome
Geometric Mean Titer of SARS-CoV-2 serum neutralizing antibodies
Time frame: 28 days after vaccination
The primary outcome measure is the vaccine (humoral) immunogenicity at 28 days after the booster dose of BNT162b2 in individuals who have previously received two doses of any inactivated COVID-19 vaccines, measured as geometric mean titer (GMT) of SARS-CoV-2 serum neutralizing antibodies using plaque reduction neutralization test (PRNT).
4 secondary outcomes
Geometric Mean Titer of SARS-CoV-2 serum neutralizing antibodies
Time frame: 182 and 365 days after vaccination
The geometric mean fold rise (GMFR) of SARS-CoV-2 serum neutralizing antibody titers from baseline to each post-vaccination timepoint measured.
Time frame: Day 28, 49, 182 and 365 after vaccination
Reactogenicity
Time frame: 7 days after vaccination or until the last symptom disappears
Hospitalizations from any cause
Time frame: 365 days after vaccination
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 15 May 2026.
- Derived from this study: PubMed 39276621Shiu EYC, Cheng SMS, Martin-Sanchez M, Au NYM, Chan KCK, Li JKC, Fung LWC, Luk LLH, Chaothai S, Kwan TC, Ip DKM, Leung GM, Poon LLM, Peiris JSM, Leung NHL, Cowling BJ. Durability for 12 months of antibody response to a booster dose of monovalent BNT162b2 in adults who had initially received 2 doses of inactivated vaccine. Vaccine. 2024 Dec 2;42(26):126317. doi: 10.1016/j.vaccine.2024.126317. Epub 2024 Sep 13.
- Derived from this study: PubMed 35675370Leung NHL, Cheng SMS, Martin-Sanchez M, Au NYM, Ng YY, Luk LLH, Chan KCK, Li JKC, Leung YWY, Tsang LCH, Chaothai S, Kwan KKH, Ip DKM, Poon LLM, Leung GM, Peiris JSM, Cowling BJ. Immunogenicity of a Third Dose of BNT162b2 to Ancestral Severe Acute Respiratory Syndrome Coronavirus 2 and the Omicron Variant in Adults Who Received 2 Doses of Inactivated Vaccine. Clin Infect Dis. 2023 Feb 8;76(3):e299-e307. doi: 10.1093/cid/ciac458.
- Individual participant dataSharing planned: Yes
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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.
Benjamin J Cowling, PhD principal investigator
The University of Hong Kong
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 BNT162b2 in people with COVID 19 Vaccine, run by The University of Hong Kong at 1 site in Hong Kong.
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 7 inclusion and 6 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 15 May 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 Hong Kong. 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?
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?
Geometric Mean Titer of SARS-CoV-2 serum neutralizing antibodies (time frame: 28 days after vaccination). 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 NCT05057182, which also lists 2 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 15 May 2026.