Abstract

SARS-CoV-2, the causative agent of COVID-19, has imposed a major threat to public health, which requires effective therapeutic and vaccination strategies. Several potential vaccine candidates that are rapidly being developed are under clinical evaluation. Considering the crucial role of the SARS-CoV-2 spike (S) glycoprotein in virus binding, entry, and induction of neutralizing antibodies, the S protein is being widely used as a target for vaccine development.

Building on advances in techniques for vaccine design, inactivated, live vectored, nucleic acid, and recombinant COVID-19 vaccines are being developed and tested for efficacy. Phase 3 clinical trials are underway or will begin soon for several of these vaccines. Assuming the clinical efficacy of one or more vaccines is demonstrated, safety is an important consideration before distributing such vaccines to the public. The current review focuses on recent advances in recombinant COVID-19 vaccine research and development and associated issues.

Keywords:

COVID-19, SARS-CoV-2, vaccine, recombinant vaccine, efficacy and safety

Inactivated vaccine against coronavirus

The development of inactivated vaccines requires the initial inactivation of a target virus, either chemically or by irradiation. This allows the nucleic acids of the virus to be destroyed, keeping the viral antigens intact. The immunological characteristics and efficacy of inactivated CoV vaccines were investigated in animal models during the emergence of the first SARS virus. An inactivated SARS-CoV vaccine was first tested in rhesus monkeys and was found to induce humoral and mucosal immunity, highlighting its potential for use in clinical trials.

Developed using sequential exposure to formaldehyde and ultraviolet radiation to ensure safe use. The immunogenicity of this vaccine was verified using a mouse model, which showed high titers of antibodies against the CoV S protein and enhanced neutralizing antibodies, highlighting its potential application as a platform for the development of a vaccine against SARS-CoV-2. Recently Gao et al (2020) developed PiCoVacc, a purified and inactivated SARS-CoV-2 virus vaccine, which was found to elicit SARS-CoV-2-specific neutralizing antibodies in mice, rats, and non-human primates.

The generated antibodies were found to neutralize 10 representative strains of SARS-CoV-2, maintaining their broad applicability against the virus. answers Currently, Sinovac Biotech has obtained approval in China to conduct a human clinical trial using an inactivated vaccine candidate against SARS-CoV-2. Beijing Institute of Biologicals/Wuhan Institute of Biologicals, Disease Research Foundation Osaka University Microbial Research Institute (BIKEN), and the National Institutes of Biomedical Innovation, Health and Nutrition (NIBIOHN) are also working on the development of inactivated vaccines.