Variants of SARS Coronavirus-2 and Their Potential Impact on the Future of the COVID-19 Pandemic

Xin Li,Kwok-Yung Yuen,Kelvin Kai-Wang To

doi:10.15212/zoonoses-2021-1003

Xin Li, Kwok-Yung Yuen + Show 1 more

Open Access

https://doi.org/10.15212/zoonoses-2021-1003

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Abstract

The emergence of SARS-CoV-2 variants of concern (VOCs), especially the sweeping spread of the delta variant, and differing public health management strategies, have rendered global eradication of SARS-CoV-2 unlikely. The currently available COVID-19 vaccines, including the inactivated whole virus vaccines, mRNA vaccines, and adenovirus-vectored vaccines, are effective in protecting people from severe disease and death from COVID-19, but they may not confer good mucosal immunity to prevent the establishment of infection and subsequent viral shedding and transmission. Mucosal vaccines delivered via intranasal route may provide a promising direction, which, if given as a third dose after a two-dose series of intramuscular vaccination, likely promotes mucosal immunity in addition to boosting the systemic cell-mediated immunity and antibody response. However, immunity induced by vaccination, and natural infection as well, is likely to wane followed by re-infection as in the case of human coronaviruses OC43, 229E, NL63, and HKU1. It is a challenge to prevent and control COVID-19 worldwide with the increasing number of VOCs associated with increased transmissibility and changing antigenicity. Nevertheless, we may seek to end the current pandemic situation through mass vaccination and gradual relaxation of non-pharmaceutical measures, which would limit the incidence of severe COVID-19. Repeated doses of booster vaccine will likely be required, similar to influenza virus, especially for the elderly and the immunocompromised patients who are most vulnerable to infection.

Highlights

The emergence of SARS-CoV-2 variants of concern (VOCs), especially the sweeping spread of the delta variant, and differing public health management strategies, have rendered global eradication of SARS-CoV-2 unlikely
The phenotypic implications of many of these mutations have not been defined, except for those affecting the surface spike protein, which is responsible for cell entry through binding to the host receptor angiotensin converting enzyme 2 (ACE2) [4] and subsequent fusion of the viral lipid envelope with the host cell membrane [5]
Before jumping to humans [6,7], definitive evidence remains lacking [8].The mutation T372A in the spike receptor binding domain (RBD) has been proposed to be a key mutation in the adaption of SARS-CoV-2 to infect humans, because this mutation has been found only in SARS-CoV-2 but not in closely related viruses such as the bat SARS-related coronavirus RaTG13 [9]. Another important example of spike mutation resulting in better adaptation of the virus to humans is the spike D614G, which was not isolated from the initial outbreak

Summary

Introduction

The emergence of SARS-CoV-2 variants of concern (VOCs), especially the sweeping spread of the delta variant, and differing public health management strategies, have rendered global eradication of SARS-CoV-2 unlikely. Few genetic mutations at the receptor binding domain were observed in the early months of the pandemic, by late 2020, many SARS-CoV-2 variants of concern (VOCs) or variants of interest (VOIs) had emerged.

Results

Conclusion