COVID-19 VaccinesPhase 2/3ARCT-154-01NCT05012943

The ARCT-154 Self-Amplifying RNA Vaccine Efficacy Study (ARCT-154-01)

A Phase 2/3 study testing ARCT-154 Self-Amplifying RNA SARS-CoV-2 Vaccine and Astra Zeneca COVID-19 vaccine in people with COVID-19 Vaccines, run by Vinbiocare Biotechnology Joint Stock Company at 3 sites in Vietnam.

Completed

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

Official record

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Trial summary

This is a Phase 1/2/3, randomized, placebo-controlled, observer-blind study designed to evaluate the safety, immunogenicity and efficacy of ARCT-154 in adult participants to be enrolled in Vietnam. Read more about this study

Who is it for?: Ages 18 to 100 yearsHealthy volunteers can take part
Conditions the study is for: COVID-19 Vaccines
What is being tested?: ARCT-154 Self-Amplifying RNA SARS-CoV-2 Vaccine and Astra Zeneca COVID-19 vaccine
Type of treatment: Vaccines
Could I receive a placebo?: Yes, some participants may receive a placebo
How many people: 19,474 participants
Where: 3 sitesVietnam
Study dates: 15 Aug 2021to 18 Jan 2023
Phase: Phase 2/3
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 to 100 years
All sexes
Healthy volunteers accepted
Adult, Older adult

Who may be able to join

Individuals who:
are able to provide consent
agree to comply with all study visits and procedures
are of childbearing potential and sexually active must be willing to adhere to contraceptive requirements
are male or female ≥18 years of age (or, for Phase 1, 18 to < 60 years of age)
are at higher risk of developing COVID-19 based on where they work or live

Who cannot join

Individuals who:
Significant infection or other acute illness, including body temperature >100.4°F (>38.0°C) on the day prior to or Day 1. Participants meeting this criterion may be rescheduled within the relevant window periods. Afebrile participants with minor illnesses can be enrolled at the discretion of the investigator.
Pregnant or breastfeeding.
Known history of COVID-19 (asymptomatic SARS-CoV-2 infection and/or nucleocapsid positive test is not exclusionary).
Close contact with a person known to be SARS-CoV-2 positive or with a clinical diagnosis of COVID-19 within 7 days prior to enrollment. Participants meeting this criterion who remain asymptomatic for 7 days may be rescheduled for enrollment within the relevant windows.
Known history of anaphylaxis, urticaria, or other significant adverse reaction to the vaccine or its excipients.

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Known history of anaphylaxis to other vaccines.
Bleeding disorder considered a contraindication to intramuscular (IM) injection or phlebotomy.
Immunosuppressive or immunodeficient state, asplenia, recurrent severe infections, or known to be HIV positive.
An underlying clinically significant acute or chronic medical condition or physical examination findings for which, in the opinion of the investigator, participation would not be in the best interest of the participant (eg, compromise the well-being) or that could prevent, limit, or confound the protocol-specified assessments.
Prior/Concomitant Therapy
Has previously received investigational or approved MERS-CoV, SARS-CoV, SARS-CoV-2 vaccines or who have plans to receive off-study COVID-19 vaccines.
Has received a live replicating vaccine within 28 days prior to each study vaccination or a licensed inactivated or non-replicating vaccine within 14 days prior to first study vaccination.
Has received treatment with immunosuppressive therapy, including cytotoxic agents or systemic corticosteroids, eg, for cancer or an autoimmune disease, within 6 months prior to Screening, or planned receipt throughout the study. If systemic corticosteroids have been administered short term (<14 days) for treatment of an acute illness, participants should not be enrolled into the study until corticosteroid therapy has been discontinued for at least 28 days prior to first study vaccine administration. Inhaled/nebulized, intra-articular, intrabursal, or topical (skin or eyes) corticosteroids are permitted.
Has received systemic immunoglobulins or blood products within 3 months prior to first study vaccine administration or plans to receive such products during the study.
Other Exclusions
Demonstrated inability to comply with the study procedures.
Investigator site staff members, employees of the Sponsor or the CRO directly involved in the conduct of the study, or site staff members otherwise supervised by the investigator, or immediate family members of any of the previously mentioned individuals.
Other restrictions apply to Phase 1 participants to ensure they are healthy.
Additional Exclusion Criteria for Phase 3c Participants Only:
No contraindications (as specified in the prescribing information) to receiving the ChAdOx1 vaccine.

Trial locations and contacts

3 sites in 1 country.

Vietnam3 sites

Hanoi Medical University
Hanoi, Hanoi, 00000
Military Medical University
Hanoi, Hanoi, 00000
Pasteur Institute
Ho Chi Minh City, Ho Chi Minh, 00000

Other trials in Vietnam

About this study

Official title: A Randomized, Observer-Blind, Controlled Study to Assess the Safety, Immunogenicity and Efficacy of the SARS-CoV-2 Self- Amplifying RNA Vaccine ARCT-154 in Adults

This is a Phase 1/2/3, randomized, placebo-controlled, observer-blind study designed to evaluate the safety, immunogenicity and efficacy of ARCT-154 in adult participants to be enrolled in Vietnam.

This study consists of four parts:

Part 1 (Phase 1) will evaluate the safety of the study vaccines in 100 healthy individuals.

Part 2 (Phase 2) will evaluate the safety and immunogenicity of the study vaccines in 300 healthy individuals.

Part 3 (Phase 3a) will evaluate the safety, immunogenicity, and efficacy of the study vaccines in 600 individuals with and without underlying medical conditions.

Part 4 (Phase 3b) will evaluate the safety and efficacy of the study vaccines in 16,000 individuals with and without underlying medical conditions.

Part 5 (Phase 3c) will evaluate the safety and non-inferiority in immunogenicity of ARCT-154 vaccine vs. Astra Zeneca COVID-19 vaccine (ChAdOx1 nCoV-19) in 2400 individuals with and without underlying medical conditions.

In Phase 1, healthy individuals 18 to < 60 years of age will be enrolled. In Phase 2, 3a, and 3b, individuals 18 years of age and older will be enrolled including individuals with underlying medical conditions that put them at higher risk of complications of COVID-19 disease.

Phase 1, Phase 2, Phase 3a and Phase 3b participants will be randomly assigned to a study group that will receive up to 2 vaccination series. Each vaccination series comprises two vaccinations at 28-day intervals: an initial vaccination series with vaccinations on Day 1 and Day 29 and an additional vaccination series around 2 months after the first series (on Day 92 and 120).

Participants of Phase 2, 3a who received 2 doses of ARCT-154 vaccine will be rerandomized to receive either dose 3 of ARCT-154 on Day 92 plus placebo on Day 120 or placebo on Day 92 plus placebo on Day 120.

For Phase 1, Phase 3b and participants in Phase 2 and 3a that received placebo in the first vaccination series, the participants will be switched over to the opposite vaccine in the second series.

There is no second vaccination series for Phase 3c as all participants receive active vaccine in the initial series.

Read the detailed description

Phase 1 will enroll 100 healthy participants that are randomly assigned 3:1 to receive ARCT-154 or placebo (75:25) for the initial series of vaccinations.

In Phase 2, 300 participants will be randomly assigned 3:1 to receive ARCT-154 or placebo for the initial series of vaccinations. Participants that received ARCT-154 in the initial series will be rerandomized 3:1 to receive ARCT or placebo on Day 92 followed by placebo on Day 120.

In Phase 3a, 600 participants will be randomly assigned 3:1 to receive ARCT-154 or placebo for the initial series of vaccinations. Participants that received ARCT-154 in the initial series will be rerandomized 3:1 to receive ARCT or placebo on Day 92 followed by placebo on Day 120.

In Phase 3b, ~16,000 participants will be randomly assigned 1:1 to receive ARCT-154 or placebo for the initial series of vaccinations.

In Phase 3c, ~2,400 participants will be randomly assigned 1:1 to receive ARCT-154 or Astra Zeneca COVID-19 vaccine. Blood samples will be collected and reserved for Immunogenicity evaluation for the first 1500 participants (3c-1) and assays for immunogenicity evaluation will be performed for the first 800 participants.

Phase 1 participants must be <60 years of age and healthy. Phase 2, 3a, and 3b and 3c participants will include elderly (≥60 years) and those with comorbidities.

For Phase 2, 3a, 3b and 3c, prior to randomization, participants will be stratified by age (< 60 or ≥ 60 years of age) and for participants < 60 years of age by risk of severe COVID 19. Participants will be followed up for approximately 1 year after completion of the initial vaccination series.

An independent Data and Safety Monitoring Board (DSMB) will perform ongoing review of blinded and unblinded data.

An independent blinded adjudication committee will adjudicate all suspected COVID-19 cases to determine if they meet the primary endpoint requirements.

Conditions: COVID-19 Vaccines
Being tested: ARCT-154 Self-Amplifying RNA SARS-CoV-2 Vaccine, Placebo (normal saline), Astra Zeneca COVID-19 vaccine
Keywords: ARCT-154, COVID-19, SARS-CoV-2, Immunogenicity, Efficacy
Medical subject headings: COVID-19

What participants receive

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

ARCT-154 Self-Amplifying RNA SARS-CoV-2 VaccineBiological
ARCT-154 Self-Amplifying RNA SARS-CoV-2 Vaccine
Placebo (normal saline)Other
Normal saline with the same volume as of ARCT-154
Astra Zeneca COVID-19 vaccineBiological
Astra Zeneca COVID-19 vaccine (ChAdOx1 nCoV-19)

Study groups in NCT05012943
Study group	Role	What they receive
ARCT-154	Experimental	Each participant is planned to receive a two-dose vaccination series of ARCT-154 at a dose of 5 µg with 28 day interval in the first vaccination series. Receives: Biological: ARCT-154 Self-Amplifying RNA SARS-CoV-2 Vaccine
Placebo	Placebo comparator	Each participant is planned to receive a two-dose vaccination series of placebo (normal saline) with 28 day interval in the first vaccination series. Receives: Other: Placebo (normal saline)
Astra Zeneca COVID-19 vaccine	Active comparator	Each participant is planned to receive a two-dose vaccination series of Astra Zeneca COVID-19 vaccine with 28 day interval in the first vaccination series. Receives: Biological: Astra Zeneca COVID-19 vaccine

What is being measured

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

Number of Participants Reporting Solicited Local Adverse Reactions (ARs)
Solicited local ARs included injection site erythema, injection site pain, injection site induration/swelling, and injection site tenderness. A summary of serious and all other non-serious adverse events regardless of causality is located in the Reported Adverse Events module.
Measured: Within 7 days after Dose 1 and Dose 2 (up to Day 7 and 36)
Number of Participants Reporting Solicited Systemic ARs
Solicited systemic ARs included arthralgia, chills, diarrhea, dizziness, fatigue, fever (categorized by measured body temperature), headache, myalgia, and nausea/vomiting. A summary of serious and all other non-serious adverse events regardless of causality is located in the Reported Adverse Events module.
Measured: Within 7 days after Dose 1 and Dose 2 (up to Day 7 and 36)
Number of Participants Reporting Unsolicited Adverse Events (AEs)
Unsolicited AEs were defined as any spontaneously reported or discovered AE. A summary of serious and all other non-serious adverse events regardless of causality is located in the Reported Adverse Events module.
Measured: Approximately 28 days after Dose 1 and Dose 2 (Day 1 to Day 29 and Day 29 to Day 57)
Number of Participants Reporting Medically Attended Adverse Events (MAAEs), Serious Adverse Events (SAEs) and AEs Leading to Discontinuation
An MAAE was defined as an AE that led to an unscheduled visit (including a telemedicine visit) with a healthcare provider ([HCP], e.g., nurse, nurse practitioner, physician's assistant, physician). An SAE was defined as any event that resulted in death, was immediately life-threatening, required inpatient hospitalization or prolongation of existing hospitalization, resulted in persistent or significant disability/incapacity or was a congenital anomaly/birth defect arising from a pregnancy conceived after receipt of study vaccine. A summary of serious and all other non-serious adverse events regardless of causality is located in the Reported Adverse Events module.
Measured: Day 1 to Day 92
Number of Participants With Neutralizing Antibody (NAb) Responses
Data are presented for the number of participants with a NAb seroconversion response as determined by the surrogate virus neutralization test (sVNT). Seroconversion was defined as a ≥4-fold increase in antibody concentration from baseline.
Measured: Day 57
Number of Participants With a First Occurrence of Coronavirus Disease 2019 (COVID-19)
COVID-19 was defined as a positive SARS-CoV-2 test and at least one of the following that was a new or worsening finding: ⦁ Fever or chills ⦁ Cough ⦁ Shortness of breath or difficulty breathing ⦁ Fatigue ⦁ Muscle or body aches ⦁ Headache ⦁ New loss of taste or smell ⦁ Sore throat ⦁ Congestion or runny nose ⦁ Nausea or vomiting ⦁ Diarrhea Data are presented for the number of participants with a first occurrence of COVID-19 with no evidence of prior infection.
Measured: Day 36 to Day 92

Secondary outcomes (11)

Geometric Mean Titers of SARS-CoV-2 Neutralizing Antibodies
Measured: Days 1, 29, 57 and 92
Geometric Mean Fold Rise in SARS-CoV-2 Neutralizing Antibody Titers
Measured: Days 29, 57, 92
Number of Participants Seroconverting for Neutralizing Antibodies
Seroconversion was defined as a ≥4-fold increase in antibody concentration from baseline as measured by the sVNT test. Data are presented for the number of participants seroconverting for neutralizing antibodies.
Measured: Days 29, 57 and 92
Geometric Mean Concentration of Spike Protein Immunoglobulin G (IgG) Binding Antibodies
Measured: Days 1, 29, 57, 92
Geometric Mean Fold Ratio of Spike Protein IgG Binding Antibodies
Measured: Days 29, 57, 92
Number of Participants Seroconverting for Spike Protein IgG Binding Antibodies
Seroconversion was defined as a ≥4-fold increase in antibody concentration from baseline. Data are presented for the number of participants seroconverting for spike protein IgG binding antibodies.
Measured: Days 29, 57, 92
Number of Participants Seroconverting on Neutralizing Antibody Responses by Plaque Reduction Neutralization Test at 50% Reduction (PRNT50)
The plaque reduction neutralization test (PRNT) is a live virus assay. Neutralizing antibody titers were calculated as the highest serum dilution that resulted in 50% reduction in the number of virus plaques (PRNT50). Data presented is for the ancestral-clinical isolate variant. Data are presented for the number of participants that demonstrated seroconversion (as defined by 4-fold increase in neutralizing antibody concentration from baseline) on PRNT50.
Measured: Days 29 and 57
Number of Participants With a First Occurrence of Severe COVID-19
Number of participants with a first occurrence of severe COVID-19 in participants with no evidence of prior infection. Severe COVID-19 was defined as a positive SARS-CoV-2 test, symptoms per protocol-defined COVID-19 and any of the following: Clinical signs at rest indicative of severe systemic illness: - Respiratory rate ≥30 per minute, - Heart rate ≥125 per minute, - Oxygen saturation (SpO2) ≤93% on room air at sea level or partial pressure of oxygen (PO2)/fraction of inspired oxygen (FiO2) <300 millimeter of mercury (mm Hg) - Respiratory failure (defined as needing high flow oxygen, noninvasive ventilation, mechanical ventilation or extracorporeal membrane oxygenation [ECMO]); Evidence of shock: - Systolic blood pressure (SBP) <90 mm Hg, or - Diastolic blood pressure (DBP) <60 mm Hg, or requiring vasopressors, - Significant acute renal, hepatic, or neurologic dysfunction - Admission to an intensive care unit (ICU) - Death
Measured: Day 36 to Day 92
Number of Participants With Death Due to COVID-19
Number of participants with death due to COVID-19 in participants with no evidence of prior infection.
Measured: Day 36 to Day 92
Number of Participants With a First Occurrence of COVID-19 Irrespective of Prior Infection
Number of participants with a first occurrence of COVID-19 irrespective of prior infection.
Measured: Day 36 to Day 92
Number of Participants With a First Occurrence of COVID-19
Number of participants with a first occurrence of COVID-19 in participants with no evidence of prior infection.
Measured: Day 1 to Day 92

Timeline

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

15 Aug 202118 Jan 2023

First posted19 Aug 2021
Study start15 Aug 2021
Primary completion18 Jan 2023
Study completion18 Jan 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.
Other trials for COVID-19 VaccinesStudies of the same condition, open and under way.
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 2/3
Primary purpose: Prevention
Allocation: Randomised
Intervention model: Parallel groups
Model description: Phase 1, 2, 3a, 3b: Participants will be randomly assigned to a study group that will receive up to 2 vaccination series. Each vaccination series comprises two vaccinations at 28-day intervals: an initial vaccination series with vaccinations on Day 1 and Day 29 and an additional vaccination series at around 2 months after the first series on Day 92 and 120. Each participant is planned to receive a two-dose vaccination series of ARCT-154 at a dose of 5 µg or a two-dose vaccination series of placebo (saline) in the first series. Participants in Phase 2, 3a who received 2 doses of ARCT-154 vaccine in the first vaccine series will be rerandomized to receive either dose 3 of ARCT-154 on Day 92 plus placebo on Day 120 or placebo on Day 92 plus placebo on Day 120. Phase 3c: Participants will be randomly assigned to a study group to receive two-dose vaccination series of ARCT-154 at a dose of 5 µg or approved COVID-19 vaccine comparator (Astra Zeneca's COVID-19 vaccine).
Masking: Triple blind
Who is masked: Participant, Investigator, Outcomes assessor
Enrolment: 19,474 participants (actual)

IDs, dates and publications

ClinicalTrials.gov ID: NCT05012943
Sponsor's protocol ID: ARCT-154-01
Acronym: ARCT-154-01
Status last verified: Oct 2025
First submitted: 13 Aug 2021
Last updated: 6 Nov 2025
Results posted: Yes, on ClinicalTrials.gov
Data monitoring committee: Yes
FDA-regulated drug: Yes
FDA-regulated device: No
Individual data sharing: No: IPD is the sole property of VinBioCare. VinBioCare may share a copy of the study IPD with their collaborative partners if requested.

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?

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Study at a glance

From the registry record, last updated by the sponsor on 6 Nov 2025. Recruitment status is as the sponsor reported it: confirm with the study team.

Official title: A Randomized, Observer-Blind, Controlled Study to Assess the Safety, Immunogenicity and Efficacy of the SARS-CoV-2 Self- Amplifying RNA Vaccine ARCT-154 in Adults
ClinicalTrials.gov ID: NCT05012943
Acronym / sponsor ID: ARCT-154-01 / ARCT-154-01
Conditions: COVID-19 Vaccines
Keywords: ARCT-154, COVID-19, SARS-CoV-2, Immunogenicity, Efficacy
Phase: Phase 2/3
Study type: Interventional
Recruitment status: Completed
Enrolment: 19,474 participants (actual)
Lead sponsor: Vinbiocare Biotechnology Joint Stock CompanyIndustry (pharma, biotech, devices)
Collaborators: Arcturus Therapeutics, Inc.
Study start: 15 Aug 2021 (actual)
Primary completion: 18 Jan 2023 (actual)
Study completion: 18 Jan 2023 (actual)
First posted: 19 Aug 2021 (actual)
Results: Posted 6 Nov 2025

Clinical summary

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

This is a Phase 1/2/3, randomized, placebo-controlled, observer-blind study designed to evaluate the safety, immunogenicity and efficacy of ARCT-154 in adult participants to be enrolled in Vietnam.

This study consists of four parts:

Part 1 (Phase 1) will evaluate the safety of the study vaccines in 100 healthy individuals.

Part 2 (Phase 2) will evaluate the safety and immunogenicity of the study vaccines in 300 healthy individuals.

Part 3 (Phase 3a) will evaluate the safety, immunogenicity, and efficacy of the study vaccines in 600 individuals with and without underlying medical conditions.

Part 4 (Phase 3b) will evaluate the safety and efficacy of the study vaccines in 16,000 individuals with and without underlying medical conditions.

For Phase 1, Phase 3b and participants in Phase 2 and 3a that received placebo in the first vaccination series, the participants will be switched over to the opposite vaccine in the second series.

There is no second vaccination series for Phase 3c as all participants receive active vaccine in the initial series.

Detailed description

Phase 1 will enroll 100 healthy participants that are randomly assigned 3:1 to receive ARCT-154 or placebo (75:25) for the initial series of vaccinations.

In Phase 3b, ~16,000 participants will be randomly assigned 1:1 to receive ARCT-154 or placebo for the initial series of vaccinations.

Phase 1 participants must be <60 years of age and healthy. Phase 2, 3a, and 3b and 3c participants will include elderly (≥60 years) and those with comorbidities.

An independent Data and Safety Monitoring Board (DSMB) will perform ongoing review of blinded and unblinded data.

An independent blinded adjudication committee will adjudicate all suspected COVID-19 cases to determine if they meet the primary endpoint requirements.

Study design

Primary purpose: Prevention
Allocation: Randomised
Intervention model: Parallel groups
Masking: Triple blind (participant, investigator, outcomes assessor)
Number of arms: 3
Model description: Phase 1, 2, 3a, 3b: Participants will be randomly assigned to a study group that will receive up to 2 vaccination series. Each vaccination series comprises two vaccinations at 28-day intervals: an initial vaccination series with vaccinations on Day 1 and Day 29 and an additional vaccination series at around 2 months after the first series on Day 92 and 120. Each participant is planned to receive a two-dose vaccination series of ARCT-154 at a dose of 5 µg or a two-dose vaccination series of placebo (saline) in the first series. Participants in Phase 2, 3a who received 2 doses of ARCT-154 vaccine in the first vaccine series will be rerandomized to receive either dose 3 of ARCT-154 on Day 92 plus placebo on Day 120 or placebo on Day 92 plus placebo on Day 120. Phase 3c: Participants will be randomly assigned to a study group to receive two-dose vaccination series of ARCT-154 at a dose of 5 µg or approved COVID-19 vaccine comparator (Astra Zeneca's COVID-19 vaccine).

Arm	Type	Receives
ARCT-154	Experimental	Biological: ARCT-154 Self-Amplifying RNA SARS-CoV-2 VaccineEach participant is planned to receive a two-dose vaccination series of ARCT-154 at a dose of 5 µg with 28 day interval in the first vaccination series.
Placebo	Placebo comparator	Other: Placebo (normal saline)Each participant is planned to receive a two-dose vaccination series of placebo (normal saline) with 28 day interval in the first vaccination series.
Astra Zeneca COVID-19 vaccine	Active comparator	Biological: Astra Zeneca COVID-19 vaccineEach participant is planned to receive a two-dose vaccination series of Astra Zeneca COVID-19 vaccine with 28 day interval in the first vaccination series.

Who may qualify

Ages: 18 to 100 years
Sex: All
Healthy volunteers: Accepted
Age groups: Adult, Older adult

Key inclusion criteria (6 listed)

are able to provide consent
agree to comply with all study visits and procedures
are of childbearing potential and sexually active must be willing to adhere to contraceptive requirements
are male or female ≥18 years of age (or, for Phase 1, 18 to < 60 years of age)
are at higher risk of developing COVID-19 based on where they work or live

Key exclusion criteria (21 listed)

Significant infection or other acute illness, including body temperature >100.4°F (>38.0°C) on the day prior to or Day 1. Participants meeting this criterion may be rescheduled within the relevant window periods. Afebrile participants with minor illnesses can be enrolled at the discretion of the investigator.
Pregnant or breastfeeding.
Known history of COVID-19 (asymptomatic SARS-CoV-2 infection and/or nucleocapsid positive test is not exclusionary).
Close contact with a person known to be SARS-CoV-2 positive or with a clinical diagnosis of COVID-19 within 7 days prior to enrollment. Participants meeting this criterion who remain asymptomatic for 7 days may be rescheduled for enrollment within the relevant windows.
Known history of anaphylaxis, urticaria, or other significant adverse reaction to the vaccine or its excipients.

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
ARCT-154 Self-Amplifying RNA SARS-CoV-2 VaccineARCT-154 Self-Amplifying RNA SARS-CoV-2 Vaccine	Biological	ARCT-154
Placebo (normal saline)Normal saline with the same volume as of ARCT-154	Other	Placebo
Astra Zeneca COVID-19 vaccineAstra Zeneca COVID-19 vaccine (ChAdOx1 nCoV-19)	Biological	Astra Zeneca COVID-19 vaccine

Primary outcome

Number of Participants Reporting Solicited Local Adverse Reactions (ARs)
Time frame: Within 7 days after Dose 1 and Dose 2 (up to Day 7 and 36)
Solicited local ARs included injection site erythema, injection site pain, injection site induration/swelling, and injection site tenderness. A summary of serious and all other non-serious adverse events regardless of causality is located in the Reported Adverse Events module.
Number of Participants Reporting Solicited Systemic ARs
Time frame: Within 7 days after Dose 1 and Dose 2 (up to Day 7 and 36)
Solicited systemic ARs included arthralgia, chills, diarrhea, dizziness, fatigue, fever (categorized by measured body temperature), headache, myalgia, and nausea/vomiting. A summary of serious and all other non-serious adverse events regardless of causality is located in the Reported Adverse Events module.
Number of Participants Reporting Unsolicited Adverse Events (AEs)
Time frame: Approximately 28 days after Dose 1 and Dose 2 (Day 1 to Day 29 and Day 29 to Day 57)
Unsolicited AEs were defined as any spontaneously reported or discovered AE. A summary of serious and all other non-serious adverse events regardless of causality is located in the Reported Adverse Events module.
Number of Participants Reporting Medically Attended Adverse Events (MAAEs), Serious Adverse Events (SAEs) and AEs Leading to Discontinuation
Time frame: Day 1 to Day 92
An MAAE was defined as an AE that led to an unscheduled visit (including a telemedicine visit) with a healthcare provider ([HCP], e.g., nurse, nurse practitioner, physician's assistant, physician). An SAE was defined as any event that resulted in death, was immediately life-threatening, required inpatient hospitalization or prolongation of existing hospitalization, resulted in persistent or significant disability/incapacity or was a congenital anomaly/birth defect arising from a pregnancy conceived after receipt of study vaccine. A summary of serious and all other non-serious adverse events regardless of causality is located in the Reported Adverse Events module.
Number of Participants With Neutralizing Antibody (NAb) Responses
Time frame: Day 57
Data are presented for the number of participants with a NAb seroconversion response as determined by the surrogate virus neutralization test (sVNT). Seroconversion was defined as a ≥4-fold increase in antibody concentration from baseline.
Number of Participants With a First Occurrence of Coronavirus Disease 2019 (COVID-19)
Time frame: Day 36 to Day 92
COVID-19 was defined as a positive SARS-CoV-2 test and at least one of the following that was a new or worsening finding: ⦁ Fever or chills ⦁ Cough ⦁ Shortness of breath or difficulty breathing ⦁ Fatigue ⦁ Muscle or body aches ⦁ Headache ⦁ New loss of taste or smell ⦁ Sore throat ⦁ Congestion or runny nose ⦁ Nausea or vomiting ⦁ Diarrhea Data are presented for the number of participants with a first occurrence of COVID-19 with no evidence of prior infection.

11 secondary outcomes

Geometric Mean Titers of SARS-CoV-2 Neutralizing Antibodies
Time frame: Days 1, 29, 57 and 92
Geometric Mean Fold Rise in SARS-CoV-2 Neutralizing Antibody Titers
Time frame: Days 29, 57, 92
Number of Participants Seroconverting for Neutralizing Antibodies
Time frame: Days 29, 57 and 92
Geometric Mean Concentration of Spike Protein Immunoglobulin G (IgG) Binding Antibodies
Time frame: Days 1, 29, 57, 92
Geometric Mean Fold Ratio of Spike Protein IgG Binding Antibodies
Time frame: Days 29, 57, 92
Number of Participants Seroconverting for Spike Protein IgG Binding Antibodies
Time frame: Days 29, 57, 92
Number of Participants Seroconverting on Neutralizing Antibody Responses by Plaque Reduction Neutralization Test at 50% Reduction (PRNT50)
Time frame: Days 29 and 57
Number of Participants With a First Occurrence of Severe COVID-19
Time frame: Day 36 to Day 92
Number of Participants With Death Due to COVID-19
Time frame: Day 36 to Day 92
Number of Participants With a First Occurrence of COVID-19 Irrespective of Prior Infection
Time frame: Day 36 to Day 92
Number of Participants With a First Occurrence of COVID-19
Time frame: Day 1 to Day 92

Results and safety

Results posted to the registry on 6 Nov 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
Placebo	8,300	7,207
ARCT-154	9,992	8,942
Astra Zeneca COVID-19 vaccine	1,182	1,155

Primary outcome: Number of Participants Reporting Solicited Local Adverse Reactions (ARs)

Time frame: Within 7 days after Dose 1 and Dose 2 (up to Day 7 and 36). Count of participants. Unit: Participants

Measure	ARCT-154 n = 8688	Placebo n = 8151	Phase 3c: ARCT-154 n = 1182	Astra Zeneca COVID-19 vaccine n = 1180
Dose 1	4060	909	467	416
Dose 2	2852	612	286	183

Population analysed: Reactogenicity Analysis Set, all participants who received any dose of study vaccine (ARCT-154 or placebo or ChAdOx1) and provided at least 1 reactogenicity diary report. As pre-specified, data are presented pooled per treatment received for Phase 1/2/3a/3b, and separately for ARCT-154 for Phase 3c. Overall number of participants analyzed = number of participants evaluable for the endpoint. Number analyzed = number of participants with evaluable data at the specified timepoint.

Primary outcome: Number of Participants Reporting Solicited Systemic ARs

Time frame: Within 7 days after Dose 1 and Dose 2 (up to Day 7 and 36). Count of participants. Unit: Participants

Measure	ARCT-154 n = 8688	Placebo n = 8151	Phase 3c: ARCT-154 n = 1182	Astra Zeneca COVID-19 vaccine n = 1180
Dose 1	4375	2620	638	657
Dose 2	3718	1889	477	331

Primary outcome: Number of Participants Reporting Unsolicited Adverse Events (AEs)

Time frame: Approximately 28 days after Dose 1 and Dose 2 (Day 1 to Day 29 and Day 29 to Day 57). Count of participants. Unit: Participants

Measure	ARCT-154 n = 8807	Placebo n = 8294	Phase 3c: ARCT-154 n = 1186	Astra Zeneca COVID-19 vaccine n = 1180
Dose 1	1323	1198	260	252
Dose 2	1232	1311	226	225

Population analysed: Safety Analysis Set, all participants who received any dose of study vaccine (ARCT-154 or placebo or ChAdOx1). Participants were analyzed according to the study vaccine received. As pre-specified, data are presented pooled per treatment received for Phase 1/2/3a/3b, and separately for ARCT-154 for Phase 3c. Overall number of participants analyzed = number of participants evaluable for the endpoint. Number analyzed = number of participants with evaluable data at the specified timepoint.

Primary outcome: Number of Participants Reporting Medically Attended Adverse Events (MAAEs), Serious Adverse Events (SAEs) and AEs Leading to Discontinuation

Time frame: Day 1 to Day 92. Count of participants. Unit: Participants

Measure	ARCT-154 n = 8807	Placebo n = 8294	Phase 3c: ARCT-154 n = 1186	Astra Zeneca COVID-19 vaccine n = 1180
MAAEs	1132	1284	148	146
SAEs	133	217	22	35
AEs Leading to Discontinuation	6	18	0	1

11 secondary outcomes are reported in the full results.

Adverse events

Time frame: All-cause mortality and serious adverse events (AEs): Day 1 to Day 92, and Day 92 to End of Study (up to approximately Day 394). Other (non-serious) AEs for Phases 1, 2, 3a and 3b: Day 1 to Day 92, and Day 92 to End of Study (up to approximately Day 394) and other (non-serious) AEs for Phase 3c: Day 1-57.. Other adverse events reported at 1% frequency or more

Group	Serious adverse events	Other adverse events	Deaths
Phases 1, 2, 3a, 3b: ARCT-154 Day 1-92	133 of 8,807 (1.5%)	1,303 of 8,807 (14.8%)	5 of 8,807
Phases 1, 2, 3a, 3b: Placebo Day 1-92	217 of 8,294 (2.6%)	1,489 of 8,294 (18%)	16 of 8,294
Phases 1, 2, 3a, 3b: Placebo or ARCT-154 Day 92-End of Study (Day 394)	180 of 8,161 (2.2%)	1,618 of 8,161 (19.8%)	12 of 8,161
Phases 1, 2, 3a, 3b: ARCT-154 Day 92-End of Study (Day 394)	176 of 7,582 (2.3%)	1,374 of 7,582 (18.1%)	9 of 7,582
Phase 3c: ARCT-154 Day 1-92	22 of 1,186 (1.9%)	0 of 0	0 of 1,186
Phase 3c: Astra Zeneca COVID-19 vaccine Day 1-92	35 of 1,180 (3%)	0 of 0	1 of 1,180
Phase 3c: ARCT-154 Day 92- End of Study (Day 394)	64 of 1,171 (5.5%)	0 of 0	0 of 1,171
Phase 3c: Astra Zeneca COVID-19 vaccine Day 92-End of Study (Day 394)	53 of 1,168 (4.5%)	0 of 0	3 of 1,168
Phase 3c: ARCT-154 Day 1-57	0 of 0	339 of 1,186 (28.6%)	0
Phase 3c: Astra Zeneca COVID-19 vaccine Day 1-57	0 of 0	304 of 1,180 (25.8%)	0

Loading the posted results from ClinicalTrials.gov…

Research links

Official record on ClinicalTrials.govLast updated by the sponsor 6 Nov 2025.
Posted resultsParticipant flow, baseline, all outcome measures and adverse events.
Individual participant dataSharing planned: No. IPD is the sole property of VinBioCare. VinBioCare may share a copy of the study IPD with their collaborative partners if requested.

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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.

The record lists no contact. Use the official record to reach the sponsor.

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

Questions about this trial

What is this clinical trial studying?

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 6 inclusion and 21 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 6 Nov 2025. Status can change between updates, so confirm with the study contact before making plans.

Where is the study taking place?

The record lists 3 sites in Vietnam. 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. Some participants in this study may receive a placebo. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.

What does this combined phase mean?

Phase 2 studies give the treatment to a larger group to see whether it has the intended effect and to keep checking safety.

Phase 3 studies compare the treatment with the current standard treatment or a placebo in a large group, to confirm how well it works and watch for side effects.

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 6 Nov 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?

Number of Participants Reporting Solicited Local Adverse Reactions (ARs) (time frame: Within 7 days after Dose 1 and Dose 2 (up to Day 7 and 36)). The study lists 6 primary outcomes in all. 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 NCT05012943.

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 6 Nov 2025.