Delta Variant: Partially Sensitive To Vaccination, but Still Worth Global Attention

Abstract

The pandemic coronavirus disease 2019 (COVID-19) has rapidly spread to all countries worldwide. The emergence of its variants has exacerbated this problem. To date, many variants have been identified across the viral genome; the variants of concern are the focus of attention due to their higher transmissibility and resistance to vaccines, especially the delta variant. The delta variant has become the dominant severe acute respiratory syndrome novel coronavirus (SARS-CoV-2) variant worldwide, causing severe panic as it is highly infectious. A better understanding of these variants may help in the development of possible treatments and save more lives. In this study, we summarize the characteristics of the variants of concern. More importantly, we summarize the results of previous studies on the delta variant. The delta variant has a high transmissibility rate and increases the risk of hospitalization and death. However, it is partially sensitive to vaccines. In addition, nonpharmaceutical interventions are valuable during epidemics. These interventions can be used against the delta variant, but managing this variant should still be taken seriously.

Keywords: delta variant; severe acute respiratory syndrome novel coronavirus; vaccine; variants of concern.

Figure 1

Structure of SARS-CoV-2 and mutations of delta variant. (A) SARS-CoV-2 forms coated spherical particles with diameters of 100–160 nm. It contains a 27–32 kb positive ssRNA genome. Envelope glycoproteins spike protein (S), envelope (E), membrane (M), and nucleocapsid (N) are encoded by 3' terminal genome. (B) Spike protein is critical for the virus to invade the host, which is also a key focus in the research on SARS-CoV-2. S1 and S2 subunits and a transmembrane domain constitute a spike protein. Scissor cuts at the boundary of S1 and S2. RBD containing the core-RBD and RBM, and NTD are on S1, which undertakes the role of binding to the host cell receptor, especially RBD, while S2 consists of FP, CD, and CT, contributing to membrane fusion. Mutations of delta variant are marked in the figure. ssRNA: single-stranded RNA; NTD: amino-terminal domain; RBD: receptor-binding domain; RBM: receptor-binding motif; FP: fusion peptide; CD: connecting domain; TM: transmembrane domain; CT: cytoplasmic tail; SARS-CoV-2: severe acute respiratory syndrome novel coronavirus. *Detected in some sequences of delta variant, but not all.