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Completed

NCT Number: NCT07834073

Immunogenicity and Safety of a Single Dose of mRNA SARS-CoV-2 Vaccine in Chinese Adults With Hybrid Immunity

This is a multicentre post-marketing cohort study to evaluate the immunogenicity and safety of a single dose of mRNA SARS-CoV-2 vaccine SYS6006 in Chinese adults predominantly with hybrid immunity. A total of 2,052 adults aged 18 years and older who received one dose of SYS6006 were monitored for serious adverse events (SAEs) for 6 months. The first 60 participants comprised an immunogenicity subgroup, with blood samples collected before vaccination and at day 14, month 3, and month 6 post-vaccination to assess humoral and cellular immune responses.

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Key information

Conditions

COVID-19 Coronaviridae Infections Coronavirus Infections Infections Lung Diseases Nidovirales Infections Pneumonia Pneumonia, Viral RNA Virus Infections Respiratory Tract Diseases Respiratory Tract Infections Sars-CoV-2 Infection Virus Diseases

Age range

18 year and older

Sex eligibility

All sexes

Study type

Interventional

Phase

Phase 4

Primary location

Jiangsu Provincial Center for Disease Control and Prevention

Nanjing, China

About this study

This study evaluated the immunogenicity and safety of a single dose of the mRNA SARS-CoV-2 vaccine SYS6006 (CSPC Megalith Biopharmaceutical Co., Ltd, Shijiazhuang, China) in Chinese adults aged 18 years and older predominantly with hybrid immunity against COVID-19. Between May and August 2023, 2,052 adults in five cities of Jiangsu Province, China (Taizhou, Changzhou, Lianyungang, Suqian, and Wuxi) received one intramuscular dose of SYS6006 (30 μg mRNA/0.3 mL) and were followed for 6 months to monitor serious adverse events (SAEs). The first 60 participants comprised the immunogenicity subgroup; serum and peripheral blood mononuclear cells (PBMCs) were collected before vaccination and at day 14, month 3, and month 6 post-vaccination. Immunogenicity assessments included pseudovirus neutralizing antibody geometric mean titres (GMTs) against wild-type (WT), BA.4/5, and XBB.1.16; receptor-binding domain (RBD)-specific IgG and IgA; ACE2-RBD binding inhibition; Fc-mediated effector functions (ADCP, ADCC, ADNP); and IFN-γ/IL-2 ELISpot responses.

Who can participate

Healthy volunteers accepted: Yes

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

  • Adults aged 18 years and over, including the elderly over 60 years and those with general underlying diseases.
  • At least 4 months since the last SARS-CoV-2 infection (or never infected), and at least 6 months since the last COVID-19 vaccination.
  • Able and willing to comply with the study procedures and to provide written informed consent.

Exclusion criteria

  • Suspected COVID-19 symptoms on the day of enrollment (e.g., dry/sore throat, cough).
  • Positive SARS-CoV-2 antigen rapid test at enrollment.
  • Prior receipt of the first COVID-19 booster dose .
  • History of severe adverse reactions or anaphylaxis related to vaccination, or known severe allergy to any vaccine component.
  • Pregnant or lactating women.
  • Any other condition that, in the investigator's judgment, makes the individual unsuitable for the study.

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Treatment and study plan

SYS6006

Biological

Lipid nanoparticle (LNP)-encapsulated mRNA SARS-CoV-2 vaccine, 30 μg mRNA/0.3 mL, single intramuscular dose.

Primary outcomes

  1. Geometric mean titer (GMT) of neutralizing antibodies in the immunogenicity subgroup

    Time frame: 14 days after booster immunization

    Measured in the immunogenicity subgroup at 14 days after booster immunization.

  2. Incidence of serious adverse events (SAEs)

    Time frame: Within 6 months after the booster administration

    Serious adverse events monitored for 6 months after the booster administration.

Secondary outcomes

  1. Geometric mean concentration (GMC) of serum RBD-specific IgG

    Time frame: Day 14 after booster immunization

    GMC of serum RBD-specific IgG antibodies against WT and Omicron variants, measured by ELISA after booster immunization

  2. Geometric mean concentration (GMC) of serum RBD-specific IgG

    Time frame: Month 3 after booster immunization

    GMC of serum RBD-specific IgG antibodies against WT and Omicron variants, measured by ELISA after booster immunization

  3. Geometric mean concentration (GMC) of serum RBD-specific IgG

    Time frame: Month 6 after booster immunization

    GMC of serum RBD-specific IgG antibodies against WT and Omicron variants, measured by ELISA after booster immunization

  4. Geometric mean concentration (GMC) of serum RBD-specific IgA

    Time frame: Day 14 after booster immunization

    GMC of serum RBD-specific IgA antibodies against WT and Omicron variants, measured by ELISA after booster immunization

  5. Geometric mean concentration (GMC) of serum RBD-specific IgA

    Time frame: Month 3 after booster immunization

    GMC of serum RBD-specific IgA antibodies against WT and Omicron variants, measured by ELISA after booster immunization

  6. Geometric mean concentration (GMC) of serum RBD-specific IgA

    Time frame: Month 6 after booster immunization

    GMC of serum RBD-specific IgA antibodies against WT and Omicron variants, measured by ELISA after booster immunization

  7. ACE2-RBD binding inhibition rate

    Time frame: Day 14 after booster immunization

    Rate of inhibition of ACE2-RBD binding in serum, measured by surrogate virus neutralization / competitive binding assay after booster immunization.

  8. ACE2-RBD binding inhibition rate

    Time frame: Month 3 after booster immunization

    Rate of inhibition of ACE2-RBD binding in serum, measured by surrogate virus neutralization / competitive binding assay after booster immunization.

  9. ACE2-RBD binding inhibition rate

    Time frame: Month 6 after booster immunization

    Rate of inhibition of ACE2-RBD binding in serum, measured by surrogate virus neutralization / competitive binding assay after booster immunization.

  10. Antigen-specific T-cell response measured by ELISpot

    Time frame: Day 14 after booster immunization

    Frequency of antigen-specific T cells (spot-forming cells) in peripheral blood measured by ELISpot assay after booster immunization.

  11. Antigen-specific T-cell response measured by ELISpot

    Time frame: Month 3 after booster immunization

    Frequency of antigen-specific T cells (spot-forming cells) in peripheral blood measured by ELISpot assay after booster immunization.

  12. Antigen-specific T-cell response measured by ELISpot

    Time frame: Month 6 after booster immunization

    Frequency of antigen-specific T cells (spot-forming cells) in peripheral blood measured by ELISpot assay after booster immunization.

Other outcomes

  1. Antibody-dependent cellular phagocytosis (ADCP)

    Time frame: Day 14 after booster immunization

    ADCP activity induced by booster immunization against WT and Omicron variants, measured by bead-based phagocytosis assay.

  2. Antibody-dependent cellular phagocytosis (ADCP)

    Time frame: Month 3 after booster immunization

    ADCP activity induced by booster immunization against WT and Omicron variants, measured by bead-based phagocytosis assay.

  3. Antibody-dependent cellular phagocytosis (ADCP)

    Time frame: Month 6 after booster immunization

    ADCP activity induced by booster immunization against WT and Omicron variants, measured by bead-based phagocytosis assay.

  4. Antibody-dependent neutrophil phagocytosis (ADNP)

    Time frame: Day 14 after booster immunization

    ADNP activity induced by booster immunization against WT and Omicron variants, measured by neutrophil-based phagocytosis assay.

  5. Antibody-dependent neutrophil phagocytosis (ADNP)

    Time frame: Month 3 after booster immunization

    ADNP activity induced by booster immunization against WT and Omicron variants, measured by neutrophil-based phagocytosis assay.

  6. Antibody-dependent neutrophil phagocytosis (ADNP)

    Time frame: Month 6 after booster immunization

    ADNP activity induced by booster immunization against WT and Omicron variants, measured by neutrophil-based phagocytosis assay.

  7. Antibody-dependent cellular cytotoxicity (ADCC)

    Time frame: Day 14 after booster immunization

    ADCC activity induced by booster immunization against WT and Omicron variants, measured by reporter/effector-cell assay.

  8. Antibody-dependent cellular cytotoxicity (ADCC)

    Time frame: Month 3 after booster immunization

    ADCC activity induced by booster immunization against WT and Omicron variants, measured by reporter/effector-cell assay.

  9. Antibody-dependent cellular cytotoxicity (ADCC)

    Time frame: Month 6 after booster immunization

    ADCC activity induced by booster immunization against WT and Omicron variants, measured by reporter/effector-cell assay.

Sponsors and collaborators

Lead sponsor

Jiangsu Province Centers for Disease Control and Prevention

Network

Registry information

Official study title

Immunogenicity and Safety of a Single Dose of mRNA COVID-19 Vaccine in Chinese Adults With Hybrid Immunity: a Multicentre, Open-label, Single-arm, Post-marketing Study

Acronym: SYS6006

Important dates

Study start
2023
Primary completion
2024
Study completion
2024
First posted
Sep 22, 2026
Registry last updated
Sep 22, 2026

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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