The outbreak of 2019-novel coronavirus disease (COVID-19) that is caused by SARS-CoV-2 has spread rapidly. Development of SARS-CoV-2-based vaccines is urgently required. This work aims to share strategies and candidate antigens to develop safe and effective vaccines against SARS-CoV-2.
Both inactivated and attenuated virus vaccines have their own disadvantages and side effects (Table 1). Alternatively, new vaccine designs based on the putative protective antigen/peptides derived from SARS-CoV-2 should be considered.
| Vaccine strategy | Advantages | Disadvantages |
|---|---|---|
| Inactivated virus vaccines | Easy to prepare; safety; high-titer neutralizing antibodies | Potential inappropriate for highly immunosuppressed individuals |
| Attenuated virus vaccines | Rapid development; induce high immune responses | Phenotypic or genotypic reversion possible; can still cause some disease |
| Subunit vaccines | High safety; consistent production; can induce cellular and humoral immune responses; high-titer neutralizing antibodies | High cost; lower immunogenicity; require repeated doses and adjuvants |
| Viral vector vaccines | Safety; induces high cellular and humoral immune responses | Possibly present pre-existing immunity |
| DNA vaccines | Easier to design; high safety; high-titer neutralizing antibodies | Lower immune responses in humans; repeated doses may cause toxicity |
| mRNA vaccines | Easier to design; high degree of adaptability; induce strong immune responses | Highly unstable under physiological conditions |
A mature SARS-CoV-2 has four structural proteins, namely, envelope (E), membrane (M), nucleocapsid (N), and spike (S). All these proteins may serve as antigens to stimulate neutralizing antibodies and increase CD4+/CD8+ T-cell responses. However, subunit vaccines require multiple booster shots and suitable adjuvants to work, and certain subunit vaccines such as hepatitis B surface antigen, PreS1, and PreS2 may fail to yield protective response when tested clinically. The DNA and mRNA vaccines that are easier to design and proceed into clinical trials very quickly remain experimental. The viral vector-based vaccines could also be quickly constructed and used without an adjuvant. However, development of such vaccines might not start until antigens containing the neutralizing epitopes are identified.
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Shang, W., Yang, Y., Rao, Y. et al. The outbreak of SARS-CoV-2 pneumonia calls for viral vaccines. npj Vaccines Published: 06 March 2020 https://doi.org/10.1038/s41541-020-0170-0
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