A Study on the Safety and Immune Response of Investigational COVID-19 mRNA Vaccines in Healthy Adults

A Phase 2 Randomized, Active-controlled, Observer-blind Study to Assess the Safety, Reactogenicity, and Immunogenicity of a Booster Dose of Investigational COVID-19 mRNA Vaccines in Healthy Adults Who Previously Received a Complete Primary Vaccination Series With or Without Booster Dose(s)

The purpose of Part A of this study is to assess the immune response and safety of a booster dose of investigational COVID-19 mRNA vaccines in healthy adults. The study will compare the investigational vaccines to control vaccine.

The purpose of Part B of this study is to assess the immune response and safety of a booster dose of investigational COVID-19 mRNA vaccines in healthy adults. The study will compare the investigational vaccine under three different storage conditions.

Study Overview

• Status: Completed
• Conditions: COVID-19; SARS-CoV-2
• Intervention / Treatment: Biological: CV0701 mRNA COVID-19 Vaccine (Low dose); Biological: CV0701 mRNA COVID-19 Vaccine (Medium dose); Biological: CV0701 mRNA COVID-19 Vaccine (High dose); Biological: CV0601 mRNA COVID-19 Vaccine; Biological: Control vaccine; Biological: CV0801 mRNA COVID-19 Vaccine

Detailed Description

Part A:

This Phase 2 study's Part A evaluates the safety, reactogenicity, and immunogenicity of two candidate vaccines - the bivalent CV0701 and the monovalent CV0601 - in healthy adults who have received a full primary vaccination series (with or without booster doses). By including these candidates, the study will assess whether immune interference occurs between the XY spike protein and the XX spike protein antigens in the bivalent vaccine compared with the XX spike protein antigen in the monovalent vaccine. In Part A, both CV0701 and CV0601 will be compared to the Control Vaccine (that serve as a standard of care control) using a randomized, observer-blinded design.

Part B:

The purpose of Part B is to evaluate the safety and Day 29 immunogenicity of CV0801 under three storage conditions:

• Condition 1: Baseline/control
• Condition 2: Intermediate storage
• Condition 3: Maximum storage

Condition 1 serves as the control against which the performance (safety, reactogenicity, and immunogenicity) of Conditions 2 and 3 will be compared.

mRNA vaccine stability is affected by product-specific factors (e.g., molecular weight, buffer composition, lipid nanoparticle encapsulation), manufacturing factors (such as the duration the vaccine remains in liquid form during production and handling at different temperatures), and storage conditions. The impact of these factors is based on product and process knowledge as well as clinical experience.

Through Part B of this Phase 2 study, GSK and CureVac aim to develop data on how different storage conditions affect the final attributes of the vaccine in a clinical trial setting.

• Study Type: Interventional
• Enrollment (Actual): 692
• Phase: Phase 2

Contacts and Locations

Study Locations

• Australia
  • Australian Capital Territory
    • Bruce, Australian Capital Territory, Australia, 2617
      • GSK Investigational Site
  • New South Wales
    • Blacktown, New South Wales, Australia, 2148
      • GSK Investigational Site
    • Botany, New South Wales, Australia, 2019
      • GSK Investigational Site
    • Brookvale, New South Wales, Australia, 2100
      • GSK Investigational Site
    • Coffs Harbour, New South Wales, Australia, 2450
      • GSK Investigational Site
    • Darlinghurst, New South Wales, Australia, 2010
      • GSK Investigational Site
    • Kanwal, New South Wales, Australia, 2259
      • GSK Investigational Site
    • Maroubra, New South Wales, Australia, 2035
      • GSK Investigational Site
    • Merewether, New South Wales, Australia, 2291
      • GSK Investigational Site
  • Queensland
    • Blacktown, Queensland, Australia, 4006
      • GSK Investigational Site
    • Sherwood, Queensland, Australia, 4068
      • GSK Investigational Site
    • Tarragindi, Queensland, Australia, 4075
      • GSK Investigational Site
  • South Australia
    • Adelaide, South Australia, Australia, 5000
      • GSK Investigational Site
  • Victoria
    • Camberwell, Victoria, Australia, 3124
      • GSK Investigational Site
• United States
  • California
    • Sacramento, California, United States, 95864
      • GSK Investigational Site
  • Florida
    • Hollywood, Florida, United States, 33024
      • GSK Investigational Site
  • Illinois
    • Peoria, Illinois, United States, 61614-4896
      • GSK Investigational Site

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: Yes

Description

Participants are eligible to be included in the study only if all of the following criteria apply:

1. Is at least 18 years old and has achieved legal age according to local regulations in each participating country.
2. Must provide documented informed consent prior to any study procedures being performed.
3. Can and will comply with the requirements of the protocol, in the opinion of the investigator.
4. Is healthy or medically stable as determined by the investigator's judgment based on medical history, vital sign measurements, and physical examination findings. Participants with pre-existing stable disease, defined as disease not requiring significant change in therapy or hospitalization for worsening disease during the 6 weeks before enrollment, can be included.
5. Prior receipt of an mRNA COVID-19 vaccine. This may be from a completed primary vaccination series or booster dose(s) of an approved or authorized mRNA COVID-19 vaccine. The last vaccination must be an mRNA COVID-19 vaccination received at least 3 months prior to randomization.

6. If the participant is a woman of childbearing potential, the participant may be enrolled in the study, if they:

   • have practiced adequate contraception for 30 days prior to study intervention administration; and
   • have a negative pregnancy test result on the day of study intervention administration; and
   • have agreed to continue adequate contraception for 2 months after study intervention administration.

Female participants of non-childbearing potential may be enrolled in the study. Nonchildbearing potential is defined as current salpingectomy, hysterectomy, ovariectomy, or postmenopausal.

Participants are excluded from the study if any of the following criteria apply:

1. Is pregnant or has a positive pregnancy test result at Visit 1.
2. Is breastfeeding or will (re)start breastfeeding from the study intervention administration to 3 months after study intervention administration.
3. Has any medical disease or psychiatric condition that, in the opinion of the investigator, precludes study participation because it would place the participant at an unacceptable risk of injury, would render them unable to meet the requirements of the protocol or may interfere with successful completion of the study.
4. Has any history of an immunosuppressive or immunodeficient condition resulting from disease.
5. Has used immunosuppressants or other immune-modifying drugs for 14 consecutive days or more within 3 months prior to the study intervention administration. Non-systemic corticosteroids are allowed. 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 before study intervention administration.
6. Has an acute medical illness or acute febrile illness with oral temperature ≥38.0°C or ≥100.4°F within 72 hours prior to study intervention administration.
7. Has participated in another study involving any investigational product, vaccine, or device within 28 days before the study intervention administration and/or planned participation through end of study (EoS).
8. Has participated in Part A of this study.
9. Has a history of hypersensitivity or severe allergic reaction including anaphylaxis, generalized urticaria, angioedema, and other significant reactions to any previous mRNA vaccine or any component of the study intervention(s).
10. Has received or plans to receive immunoglobulins or any blood or blood products within 3 months before study intervention administration through EoS.
11. Has a bleeding disorder, or prior history of significant bleeding or bruising following intramuscular injections.
12. Has a history of chronic alcohol consumption and/or drug abuse as deemed by the investigator to render the potential participant unable/unlikely to provide accurate safety reports or comply with study procedures.
13. Has a history of myocarditis, pericarditis, or idiopathic cardiomyopathy, or presence of any medical condition that increases risk of myocarditis or pericarditis, including cocaine abuse, cardiomyopathy, endomyocardial fibrosis, hypereosinophilic syndrome, hypersensitivity myocarditis, eosinophilic granulomatosis with polyangiitis and persistent myocardial infection.
14. Has received a live vaccine 30 days before the study intervention administration or has a planned administration within 30 days after the study intervention administration.
15. Has received a non-replicating vaccine 8 days before the study intervention administration or has a planned administration within 14 days after the study intervention administration.
16. Has a documented history of confirmed SARS-CoV-2 infection within 3 months before study intervention administration.
17. Has had known close contact with anyone who had a confirmed SARS-CoV-2 infection within 2 weeks before study intervention administration.
18. Is an employee or family member of the investigator or study site staff.

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Prevention
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Triple

Number of Arms

8

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Part A: CV0701 mRNA COVID-19 Vaccine (Low dose); Participants received one dose of the CV0701 mRNA COVID-19 vaccine in the low-dose formulation on Day 1.	Biological: CV0701 mRNA COVID-19 Vaccine (Low dose); Study vaccine was administered as a single intramuscular injection.
Experimental: Part A: CV0701 mRNA COVID-19 Vaccine (Medium dose); Participants received one dose of the CV0701 mRNA COVID-19 vaccine in the medium-dose formulation on Day 1.	Biological: CV0701 mRNA COVID-19 Vaccine (Medium dose); Study vaccine was administered as a single intramuscular injection.
Experimental: Part A: CV0701 mRNA COVID-19 Vaccine (High dose); Participants received one dose of the CV0701 mRNA COVID-19 vaccine in the high-dose formulation on Day 1.	Biological: CV0701 mRNA COVID-19 Vaccine (High dose); Study vaccine was administered as a single intramuscular injection.
Experimental: Part A: CV0601 mRNA COVID-19 vaccine; Participants received one dose of the CV0601 mRNA COVID-19 vaccine on Day 1.	Biological: CV0601 mRNA COVID-19 Vaccine; Study vaccine was administered as a single intramuscular injection.
Active Comparator: Part A: Control Vaccine; Participants received one dose of the control vaccine at Day 1.	Biological: Control vaccine; Study vaccine was administered as a single intramuscular injection.
Experimental: Part B: CV0801 mRNA COVID-19 vaccine (Maximum storage condition); Participants received one dose of the CV0801 mRNA COVID-19 vaccine on Day 1 under Maximum storage condition.	Biological: CV0801 mRNA COVID-19 Vaccine; Study vaccine was administered as a single intramuscular injection.
Experimental: Part B: CV0801 mRNA COVID-19 vaccine (Intermediate storage condition); Participants received one dose of the CV0801 mRNA COVID-19 vaccine on Day 1 under Intermediate storage condition.	Biological: CV0801 mRNA COVID-19 Vaccine; Study vaccine was administered as a single intramuscular injection.
Experimental: Part B: CV0801 mRNA COVID-19 vaccine (Baseline-control storage condition); Participants received one dose of the CV0801 mRNA COVID-19 vaccine on Day 1 under Baseline-control storage condition.	Biological: CV0801 mRNA COVID-19 Vaccine; Study vaccine was administered as a single intramuscular injection.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Part A: Geometric Mean Titer (GMT) of Serum Neutralization Titers Against Pseudovirus Bearing SARS-CoV-2 Strain XX Spike Protein		At Day 29
Part A: GMT of Serum Neutralization Titers Against Pseudovirus Bearing SARS-CoV-2 Strain XY Spike Protein		At Day 29
Part B: GMT of Serum Neutralization Titers Against Pseudovirus Bearing SARS-CoV-2 Strain XY Spike Protein		At Day 29
Part A: Number of Participants Reporting Any Solicited Administration Site Adverse Events (AEs)	Assessed solicited administration site events included injection site redness (erythema), pain, swelling and lymphadenopathy (defined as localized axillary, cervical or supraclavicular swelling or tenderness ipsilateral to the injection arm). Any = occurrence of the event regardless of intensity grade.	Day 1 to Day 7
Part A: Number of Participants Reporting Any Solicited Systemic AEs	Assessed solicited systemic events included fever, chills, headache, myalgia (muscle pain), arthralgia (joint pain), and fatigue (tiredness). Fever is defined as body temperature is higher than or equal to (>=) 38ºC; preferred location for measuring the temperature is oral. Any = occurrence of the event regardless of intensity grade.	Day 1 to Day 7
Part A: Number of Participants Reporting Any Unsolicited AEs	An unsolicited AE is an AE that is either not included in the list of solicited events or can be included in the list of solicited events but with an onset outside the specified period of follow-up for solicited events. Unsolicited AEs include both serious and nonserious AEs. Any = occurrence of the event regardless of intensity grade.	Day 1 to Day 28
Part A: Number of Participants Reporting Any Medically Attended Adverse Events (MAAEs), Serious Adverse Events (SAEs) and AEs of Special Interest (AESIs)	An SAE refers to any untoward medical occurrence that results in death, is life-threatening, requires inpatient hospitalization or extends existing hospitalization, causes persistent or significant disability/incapacity, involves a congenital anomaly/birth defect in a participant's offspring, includes an abnormal pregnancy outcome, or occurs in any other situation per the investigator's judgement. An MAAE results in a visit to a medical professional, such as televisits, physician's office visits, urgent care visits, emergency rooms visits, or hospitalizations. AESIs are severe or non-severe predefined AEs of scientific and medical concern specific to the product/program. This study noted the following AESIs: potential immune-mediated disease (pIMDs), lab-confirmed moderate to severe COVID-19, myocarditis and pericarditis, anaphylaxis, or severe hypersensitivity within 24 hours post-intervention. "Any" indicates the occurrence of the event regardless of its intensity grade.	Day 1 to Day 181
Part B: Number of Participants Reporting Any Solicited Administration Site AEs	Assessed solicited administration site events included injection site redness (erythema), pain, swelling and lymphadenopathy (defined as localized axillary, cervical or supraclavicular swelling or tenderness ipsilateral to the injection arm). Any = occurrence of the event regardless of intensity grade.	Day 1 to Day 7
Part B: Number of Participants Reporting Any Solicited Systemic AEs	Assessed solicited systemic events included fever, chills, headache, myalgia (muscle pain), arthralgia (joint pain), and fatigue (tiredness). Fever is defined as body temperature >= 38ºC; preferred location for measuring the temperature is oral. Any = occurrence of the event regardless of intensity grade.	Day 1 to Day 7
Part B: Number of Participants Reporting Any Unsolicited AEs	An unsolicited AE is an AE that is either not included in the list of solicited events or can be included in the list of solicited events but with an onset outside the specified period of follow-up for solicited events. Unsolicited AEs include both serious and nonserious AEs. Any = occurrence of the event regardless of intensity grade.	Day 1 to Day 28
Part B: Number of Participants Reporting Any MAAEs, SAEs and AESIs		Day 1 to Day 181

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Part A: GMT of Serum Neutralization Titers Against Pseudovirus Bearing SARS-CoV-2 Strain XX Spike Protein		At Day 91 and Day 181
Part A: GMT of Serum Neutralization Titers Against Pseudovirus Bearing SARS-CoV-2 Strain XY Spike Protein		At Day 91 and Day 181
Part A: GMT of Serum Neutralization Titers Against Pseudovirus Bearing SARS-CoV-2 Strain XZ Spike Protein		At Day 29, Day 91 and Day 181
Part A: Percentage of Participants With Seroresponse of Serum Neutralization Titers Against Pseudovirus Bearing SARS-CoV-2 Strain XX Spike Protein	Seroresponse is defined as post-booster titer greater than or equal to (≥) 4 times the lower limit of quantification (LLOQ) when pre-vaccination titer is below LLOQ or a post-booster titer ≥ 4 times the pre-booster titer when pre-vaccination titer is ≥ LLOQ.	At Day 29 compared to baseline (Day 1)
Part A: Percentage of Participants With Seroresponse of Serum Neutralization Titers Against Pseudovirus Bearing SARS-CoV-2 Strain XY Spike Protein	Seroresponse is defined as post-booster titer ≥ 4 times the lower limit of quantification (LLOQ) when pre-vaccination titer is below LLOQ or a post-booster titer ≥ 4 times the pre-booster titer when pre-vaccination titer is ≥ LLOQ.	At Day 29 compared to baseline (Day 1)
Part A: Percentage of Participants With Seroresponse of Serum Neutralization Titers Against Pseudovirus Bearing SARS-CoV-2 Strain XZ Spike Protein	Seroresponse is defined as post-booster titer ≥ 4 times the LLOQ when pre-vaccination titer is below LLOQ or a post-booster titer ≥ 4 times the pre-booster titer when pre-vaccination titer is ≥ LLOQ.	At Day 29 compared to baseline (Day 1)
Part A: Geometric Mean Increase (GMI) of Serum Neutralization Titers Against Pseudovirus Bearing SARS-CoV-2 Strain XX Spike Protein	GMI is defined as the the geometric mean of the within participant ratios of the post-dose titer over the pre-dose titer.	At Day 29, Day 91 and Day 181 compared to baseline (Day 1)
Part A: GMI of Serum Neutralization Titers Against Pseudovirus Bearing SARS-CoV-2 Strain XY Spike Protein	GMI is defined as the the geometric mean of the within participant ratios of the post-dose titer over the pre-dose titer.	At Day 29, Day 91 and Day 181 compared to baseline (Day 1)
Part A: GMI of Serum Neutralization Titers Against Pseudovirus Bearing SARS-CoV-2 Strain XZ Spike Protein	GMI is defined as the the geometric mean of the within participant ratios of the post-dose titer over the pre-dose titer.	At Day 29, Day 91 and Day 181 compared to baseline (Day 1)

Collaborators and Investigators

• Sponsor: GlaxoSmithKline
• Collaborators: CureVac

Study record dates

Study Major Dates

• Study Start (Actual): August 1, 2023
• Primary Completion (Actual): August 30, 2024
• Study Completion (Actual): August 30, 2024

Study Registration Dates

• First Submitted: July 24, 2023
• First Submitted That Met QC Criteria: July 24, 2023
• First Posted (Actual): July 25, 2023

Study Record Updates

• Last Update Posted (Estimated): October 23, 2025
• Last Update Submitted That Met QC Criteria: October 8, 2025
• Last Verified: October 1, 2025

More Information

Terms related to this study

• Keywords: COVID-19; Pandemic; Booster vaccine
• Additional Relevant MeSH Terms: Respiratory Tract Infections; Infections; RNA Virus Infections; Virus Diseases; Respiratory Tract Diseases; Lung Diseases; Pneumonia, Viral; Pneumonia; Coronavirus Infections; Coronaviridae Infections; Nidovirales Infections; COVID-19
• Other Study ID Numbers: 219075; 2023-504596-25-00 (Other Identifier: EU CT number)

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: YES
• IPD Plan Description: Qualified researchers may request access to anonymized individual patient-level data (IPD) and related study documents of the eligible studies via the Data Sharing Portal. Details on GSK's data sharing criteria can be found at: https://www.gsk.com/en-gb/innovation/trials/data-transparency/
• IPD Sharing Time Frame: Anonymized IPD will be made available within 6 months of publication of primary, key secondary and safety results for studies in product with approved indication(s) or terminated asset(s) across all indications.
• IPD Sharing Access Criteria: Anonymized IPD is shared with researchers whose proposals are approved by an Independent Review Panel and after a Data Sharing Agreement is in place. Access is provided for an initial period of 12 months but an extension may be granted, when justified, for up to 6 months.
• IPD Sharing Supporting Information Type: STUDY_PROTOCOL; SAP; ICF; CSR

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: Yes
• Studies a U.S. FDA-regulated device product: No