Last reviewed 2026-04-23 · How we verify

SCB-2019/Clover

SCB-2019 is a recombinant protein vaccine candidate designed to stimulate immune responses against SARS-CoV-2 by presenting the spike protein receptor-binding domain.

SCB-2019 is a recombinant protein vaccine candidate designed to stimulate immune responses against SARS-CoV-2 by presenting the spike protein receptor-binding domain. Used for COVID-19 prevention in adults.

At a glance

Mechanism of action

SCB-2019 is a subunit vaccine consisting of the receptor-binding domain (RBD) of the SARS-CoV-2 spike protein produced in mammalian cells and formulated with an adjuvant. It is designed to elicit both humoral and cellular immune responses to provide protection against COVID-19 infection and severe disease.

Approved indications

• COVID-19 prevention in adults

Common side effects

• Injection site pain or erythema
• Fatigue
• Headache
• Myalgia
• Fever

Key clinical trials

• Safety and Immunogenicity Dose-finding Study of Adjuvanted SCB-2020S Vaccine in Adults (PHASE1)
• Assessment of Immunogenicity, Safety and Reactogenicity of a Booster Dose of Various COVID-19 Vaccine Platforms in Individuals Primed With Several Regimes. (PHASE3)
• An Observer-blind, Cohort Randomized, Exploratory Phase 3 Study to Evaluate the Safety and Immunogenicity of Recombinant Covid-19 Vaccine, mRNA Covid-19 Vaccine and Recombinant SARS-CoV-2 Trimeric S-protein Subunit Vaccine as 4th Dose in Individuals Primed/ Boosted With Various Regimens (PHASE3)
• Immunogenicity and Safety of Heterologous and Homologous Boosting With ChAdOx1-S and CoronaVac or a Formulation of SCB-2019 (COVID-19) (PHASE2)
• Immunogenicity and Safety of Adjuvanted SCB-2020S Vaccines in Adults (PHASE2)

Primary sources

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