Development of SARS-CoV-2 Vaccine: Challenges and Prospects

Abstract

The WHO declared coronavirus disease 2019 (COVID-19) a pandemic in March 2020, which was caused by novel coronavirus severe acute respiratory coronavirus 2 (SARS-CoV-2). SARS-CoV-2 made its first entry into the world in November 2019, and the first case was detected in Wuhan, China. Mutations in the SARS-CoV-2 genome distressed life in almost every discipline by the extended production of novel viral variants. In this article, authorized SARS-CoV-2 vaccines including mRNA vaccines, DNA vaccines, subunit vaccines, inactivated virus vaccines, viral vector vaccine, live attenuated virus vaccines and mix and match vaccines will be discussed based on their mechanism, administration, storage, stability, safety and efficacy. The information was collected from various journals via electronic searches including PubMed, Science Direct, Google Scholar and the WHO platform. This review article includes a brief summary on the pathophysiology, epidemiology, mutant variants and management strategies related to COVID-19. Due to the continuous production and unsatisfactory understanding of novel variants of SARS-CoV-2, it is important to design an effective vaccine along with long-lasting protection against variant strains by eliminating the gaps through practical and theoretical knowledge. Consequently, it is mandatory to update the literature through previous and ongoing trials of vaccines tested among various ethnicities and age groups to gain a better insight into management strategies and combat complications associated with upcoming novel variants of SARS-CoV-2.

Keywords: COVID-19; SARS-CoV-2; vaccines; variants.

Figure 1

A schematic diagram of SARS-CoV-2 genome structure. SARS-CoV-2 is an enveloped RNA virus with an approximately 30 kilo base pair (kbp) genome size. The primary structural proteins of SARS-CoV-2 are membrane (M), spike (S) and nucleocapsid (N) proteins. The genome of SARS-CoV-2 consists of 14 open reading frames (ORFs) which encode for 27 structural and non-structural proteins. This image was created with Biorender.com.

Figure 2

A schematic diagram of current active development of SARS-CoV-2 vaccines as of September 2022. There are several types of vaccines which include (A) Inactivated viral vaccines, (B) Protein subunits vaccines, (C) Adenoviral vector vaccines and (D) mRNA vaccines. Aside from the whole inactivated virus in inactivated viral vaccines, other vaccines targeted the binding domain of SARS-CoV-2 Spike (S) protein. Moreover, the vector and mRNA vaccines targeted muscle cells at the injection site. The muscle cells produced some portion of the SARS-CoV-2 S protein, which is then presented by MHC Class I to antigen-presenting cells (APCs) and cytotoxic T cells. In contrast, inactivated viral vaccines and protein subunits vaccines are directly taken up by APCs. The APCs then presented the S protein antigen to T helper cells as well as B cells, which in turn activated sequential activities of humoral and cellular immune response against the SARS-CoV-2 S protein. These immunological activities also indirectly generate memory T cells and B cells for protection against future exposure against the virus. This image was created with Biorender.com.

Figure 3

Current perspective of vaccine development against SARS-CoV-2. The figure was made with Biorender.com (accessed: 30 December 2022).