Vaccines platforms and COVID-19: what you need to know

Abstract

Background: The novel SARS-CoV-2, responsible for the COVID-19 pandemic, is the third zoonotic coronavirus since the beginning of the 21 first century, and it has taken more than 6 million human lives because of the lack of immunity causing global economic losses. Consequently, developing a vaccine against the virus represents the fastest way to finish the threat and regain some "normality."

Objective: Here, we provide information about the main features of the most important vaccine platforms, some of them already approved, to clear common doubts fostered by widespread misinformation and to reassure the public of the safety of the vaccination process and the different alternatives presented.

Methods: Articles published in open access databases until January 2022 were identified using the search terms "SARS-CoV-2," "COVID-19," "Coronavirus," "COVID-19 Vaccines," "Pandemic," COVID-19, and LMICs or their combinations.

Discussion: Traditional first-generation vaccine platforms, such as whole virus vaccines (live attenuated and inactivated virus vaccines), as well as second-generation vaccines, like protein-based vaccines (subunit and viral vector vaccines), and third-generation vaccines, such as nanoparticle and genetic vaccines (mRNA vaccines), are described.

Conclusions: SARS-CoV-2 sequence information obtained in a record time provided the basis for the fast development of a COVID-19 vaccine. The adaptability characteristic of the new generation of vaccines is changing our capability to react to emerging threats to future pandemics. Nevertheless, the slow and unfair distribution of vaccines to low- and middle-income countries and the spread of misinformation are a menace to global health since the unvaccinated will increase the chances for resurgences and the surge of new variants that can escape the current vaccines.

Keywords: Advantages and disadvantages, first–second- and third-generation vaccines; COVID-19; SARS-CoV-2; Vaccine types; Vaccines platforms; mRNA vaccines.

Fig. 1

SARS-CoV-2 full RNA genomic schematic structure with approximately 29,700 nucleotides and S protein domains. The genome encodes two large genes ORF1a encodes (nsp1–nsp10), ORF1b encodes (nsp1–nsp16), for a total of 16 non-structural proteins (nsp1– nsp16). A replicase complex comprised by ORF1a and ORF1b at the 5′UTR region. Four structural genes encode the structural proteins, spike (S), envelope (E), membrane (M), and nucleocapsid (N) proteins, and accessory proteins included among the structural proteins, that are characteristic of SARS-CoV-2 in white. A poly (A) tail at the 3′UTR. NTD: N-Terminal Domain (14–305 residues). RBD: Receptor-Binding Domain (RBD, 319–541 residues). FP: Fusion Peptide (788–806 residues). HR1: Heptapeptide Repeat Sequence 1 (HR1) (912–984 residues). TM: Transmembrane Domain (1213–1237 residues). CT: Cytoplasm Domain (1237–1273)

Fig. 2

Structure of a spherical oily coated Beta-Coronavirus. A single-stranded positive-sense RNA (30 kb) surrounded by the (S), Envelope (E), and Membrane (M), and the enlargement of a Spike Protein (S), responsible for the entrance into the host cells via Angiotensin Converting Enzyme 2 (ACE2) human receptor

Fig. 3

Main vaccines types and platforms for SARS-CoV-2

Fig. 4

SARS-CoV-2 Virion and Spike protein subunits. Subunit 1 S1-CTD (Citoplasmic Domain). S1 NTD (N-Terminal domain). S2 Subunit 2. Receptor Binding Domain [ RBD]. Angiotensin-converting enzyme 2 (ACE2)

Fig. 5

Vaccine front-runner candidates for SARS-CoV-2. Including Whole Virus, Viral Vector, Protein Based and Nucleic Vaccines