A Phase 3b/4 Randomised Trial of 3 Doses of Protein-based Covid-19 Vaccine (SpikoGen)

September 16, 2025 updated by: Vaxine Pty Ltd
This study will determine the immunogenicity of Spikogen in vaccine naïve individuals. Spikogen will be administered as two doses 1 month apart with a third booster dose either 1 or 3 months after the second dose. This study will provide key data on SARS-CoV-2 antibody responses.

Study Overview

Status

Completed

Conditions

Intervention / Treatment

Detailed Description

The SARS-CoV-2 outbreak has caused millions of deaths globally. It has a particularly high mortality rate in elderly people and those with chronic disease where mortality rates can be as high as 20-30%. SARS-COV-2 vaccines remain a key priority to help fight the current pandemic. COVID-19 vaccines prevent symptomatic infection and may help reduce virus transmission. Spikogen® vaccine, also known as Covax-19™ in Australia, is an adjuvanted recombinant protein Covid-19 vaccine has recently been approved by the Iranian FDA for emergency use in Iran in adults as a primary vaccine course and booster dose, after meeting its primary efficacy endpoint in a Phase 3 trial in 16,876 participants randomised 3:1 to receive Spikogen vaccine or saline placebo via two intramuscular doses 3 weeks apart where Spikogen vaccine demonstrated significant protection against serious infection with the delta variant. Approximately 5-10% of the broader Australian population and an even higher proportion of the indigenous populations remains unvaccinated despite current availability of these vaccines. One reason is that some people have medical contraindications to the current vaccines, such as serious allergies to the vaccine components such as polyethyleneglycol (PEG) in the mRNA vaccines.

Spikogen vaccine is made using a recombinant protein approach with the SARS-CoV-2 spike protein synthesized in an insect cell line grown in broth. Insect cell expression of recombinant protein is a well-established vaccine manufacturing approach. Spikogen vaccine also contains a unique Australian developed adjuvant called Advax-CpG55.2, which is added to the spike protein to make the vaccine more effective. AdvaxCpG55.2 has two components, one a natural plant sugar called inulin, and the second a short synthetic oligonucleotide polymer, known as CpG55.2 oligonucleotide.

Spikogen vaccine is designed to protect against SARS-CoV-2 infection. It has been shown to be effective against infection in hamster, ferret and monkey SARS-CoV-2 infection models.

This study will determine the immunogenicity of Spikogen in vaccine-naïve individuals. Spikogen will be administered as two doses 31 month apart with a third booster dose given either 1 or 3 months after the second dose.

Study Type

Interventional

Enrollment (Actual)

39

Phase

  • Phase 3

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Locations

  • Australia
    • South Australia
      • Adelaide, South Australia, Australia, 5042
        • ARASMI

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

18 years and older (Adult, Older Adult)

Accepts Healthy Volunteers

Yes

Description

Inclusion Criteria:

  • Able to provide written informed consent
  • Males or females* 18 years of age or older
  • Understand and are likely to comply with planned study procedures and be available for all study visits.
  • Have not previously had a Covid-19 vaccine and do not intend to have a non-study Covid-19 vaccine within the next 6 months

Exclusion Criteria:

  • History of Covid-19 vaccination.
  • History of serious vaccine allergy.
  • Pregnancy1
  • Have received an experimental agent within 30 days prior to the study vaccination or expect to receive another experimental agent during the trial reporting period.
  • Any medical, social or mental condition which, in the opinion of the investigator, would be detrimental to the subjects or the study.

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Prevention
  • Allocation: Randomized
  • Interventional Model: Parallel Assignment
  • Masking: None (Open Label)

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Experimental: Spikogen vaccine - accelerated arm
Spikogen vaccine 25 micrograms by intramuscular injection on study months 0, 1 and 2
Biological: Advax-CpG55.2 adjuvanted recombinant spike protein
recombinant SARS-CoV-2 spike protein formulated with Advax-CpG55.2 adjuvant
Other Names:
  • Spikogen vaccine
Experimental: Spikogen vaccine - standard arm
Spikogen vaccine 25 micrograms by intramuscular injection on study months 0, 1 and 4
Biological: Advax-CpG55.2 adjuvanted recombinant spike protein
recombinant SARS-CoV-2 spike protein formulated with Advax-CpG55.2 adjuvant
Other Names:
  • Spikogen vaccine

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
First dose Seroconversion
Time Frame: 2-4 weeks post first immunisation
Proportion of subjects in each group stratified by baseline antibody positivity seroconverting to spike protein antibody positivity
2-4 weeks post first immunisation
Second dose Seroconversion
Time Frame: 2-4 weeks post second immunisation
Proportion of subjects in each group stratified by baseline antibody positivity seroconverting to spike protein antibody positivity
2-4 weeks post second immunisation
Third Dose Seroconversion
Time Frame: 2-4 weeks post third immunisation
Proportion of subjects in each group stratified by baseline antibody positivity seroconverting to spike protein antibody positivity
2-4 weeks post third immunisation
Final Seroconversion
Time Frame: through study completion, an average of 7 months
Proportion of subjects in each group stratified by baseline antibody positivity seroconverting to spike protein antibody positivity
through study completion, an average of 7 months
First Dose GMT
Time Frame: 2-4 weeks post first immunisation
Spike protein antibody Geometric Mean Titers (GMT) in each group stratified by baseline antibody positivity
2-4 weeks post first immunisation
Second Dose GMT
Time Frame: 2-4 weeks post second immunisation
Spike protein antibody Geometric Mean Titers (GMT) in each group stratified by baseline antibody positivity
2-4 weeks post second immunisation
Third Dose GMT
Time Frame: 2-4 weeks post third immunisation
Spike protein antibody Geometric Mean Titers (GMT)in each group stratified by baseline antibody positivity
2-4 weeks post third immunisation
Final GMT
Time Frame: through study completion, an average of 7 months
Spike protein antibody Geometric Mean Titers (GMT)in each group stratified by baseline antibody positivity
through study completion, an average of 7 months
First Dose Adverse events (AE)
Time Frame: 7 days post first immunisation
AE occurring within 7 days of immunisation in each group stratified by baseline antibody positivity
7 days post first immunisation
Second Dose Adverse events (AE)
Time Frame: 7 days post second immunisation
AE occurring within 7 days of immunisation in each group stratified by baseline antibody positivity
7 days post second immunisation
Third Dose Adverse events (AE)
Time Frame: 7 days post third immunisation
AE occurring within 7 days of immunisation in each group stratified by baseline antibody positivity
7 days post third immunisation
Serious adverse events (SAE)
Time Frame: through study completion, an average of 7 months
Number of Serious adverse events (SAE) occurring within study period in each group stratified by baseline antibody positivity
through study completion, an average of 7 months

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
First dose Vaccine efficacy
Time Frame: From 2 weeks post-first dose to 2 weeks after second dose
Proportion of Covid-19 infections in trial participants in each group stratified by baseline antibody positivity
From 2 weeks post-first dose to 2 weeks after second dose
Second dose Vaccine efficacy
Time Frame: From 2 weeks post-second dose to 2 weeks after third dose
Proportion of Covid-19 infections in trial participants in each group stratified by baseline antibody positivity
From 2 weeks post-second dose to 2 weeks after third dose
Third dose Vaccine efficacy
Time Frame: From 2 weeks post-third dose through study completion, an average of 7 months
Proportion of Covid-19 infections in trial participants in each group stratified by baseline antibody positivity
From 2 weeks post-third dose through study completion, an average of 7 months
Total Covid-19 infections
Time Frame: From first vaccine dose through study completion, an average of 7 months
Proportion of breakthrough Covid-19 infections in trial participants in each group stratified by baseline antibody positivity
From first vaccine dose through study completion, an average of 7 months
Seroconversion against variants of concern
Time Frame: 2-4 weeks post first, second and third immunisation and at study completion
Serum spike protein antibody seroconversion rates against each SARS-CoV-2 variant of concern in trial participants in each group stratified by baseline antibody positivity
2-4 weeks post first, second and third immunisation and at study completion
GMT against variants of concern
Time Frame: 2-4 weeks post first, second and third immunisation and at study completion
Geometric mean serum spike protein antibodies against SARS-CoV-2 variants in trial participants in each group stratified by baseline antibody positivity
2-4 weeks post first, second and third immunisation and at study completion

Other Outcome Measures

Outcome Measure
Measure Description
Time Frame
Antibody kinetics
Time Frame: 2-4 weeks post first, second and third immunisation and at study completion
rate of change in peak to trough serum spike protein antibody levels over time in each group stratified by baseline antibody positivity
2-4 weeks post first, second and third immunisation and at study completion
Age effects on seroconversion
Time Frame: 2-4 weeks post first, second and third immunisation and at study completion
Proprotion seroconverting to spike protein antibodies analysed by age and gender
2-4 weeks post first, second and third immunisation and at study completion
Age effects on antibody levels
Time Frame: 2-4 weeks post first, second and third immunisation and at study completion
Geometric Mean Titers of spike protein antibodies in participants by age and gender
2-4 weeks post first, second and third immunisation and at study completion
immune-deficiency effects on seroconversion
Time Frame: 2-4 weeks post first, second and third immunisation and at study completion
Proportion of subjects seroconverting to spike protein antibodies in participants with or without immune-deficiency
2-4 weeks post first, second and third immunisation and at study completion
immune-deficiency effects on antibody levels
Time Frame: 2-4 weeks post first, second and third immunisation and at study completion
Geometric Mean Titers (GMT) of spike protein antibodies in participants with or without immune-deficiency
2-4 weeks post first, second and third immunisation and at study completion

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Vaxine Pty Ltd

Collaborators

Australian Respiratory and Sleep Medicine Institute

Investigators

  • Study Director: Dimitar Sajkov, MBBS, ARASMI

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

Helpful Links

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

August 15, 2022

Primary Completion (Actual)

December 31, 2023

Study Completion (Actual)

December 31, 2023

Study Registration Dates

First Submitted

March 7, 2022

First Submitted That Met QC Criteria

March 11, 2022

First Posted (Actual)

March 15, 2022

Study Record Updates

Last Update Posted (Estimated)

September 17, 2025

Last Update Submitted That Met QC Criteria

September 16, 2025

Last Verified

September 1, 2025

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • AUST-C19-P3/4

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

IPD Plan Description

There is no current plan to share IPD with other researchers, but requests for data access will be considered on a case by case basis

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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