Current vaccine strategies against SARS-CoV-2: Promises and challenges

Abstract

In the years since the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic began and spread across the globe, lessons have been learned about the challenges and opportunities that a pandemic brings to humankind. Researchers have produced many vaccines at unprecedented speed to protect people, but they have also been cognizant of the challenges presented by a new and unexpected infectious disease. The scope of this review is to examine the path of vaccine discovery so far and identify potential targets. Here, we provide insight into the leading vaccines and their advantages and challenges. We discuss the emerging mutations within the SARS-CoV-2 spike protein and other issues that need to be addressed to overcome coronavirus disease 2019 (COVID-19) completely. Future research is needed to develop a cheap, temperature-stable vaccine providing long-term immunity that protects the upper respiratory tract.

Keywords: Approved vaccines; COVID-19; SARS-CoV-2; preclinical vaccines; side effects; vaccine hesitancy; vaccine strategies; variants of concern.

Fig 1

A, Different vaccine platforms currently utilized against COVID-19. I, The SARS-CoV-2 trimer is shown in blue in addition to a virus-like particle (VLP) with the trimer anchored within the VLP membrane. II, A lipid-based vehicle containing mRNA encoding the SARS-CoV-2 S protein and a DNA plasmid also encoding the S protein used for vaccination. III, Deactivated SARS-CoV-2 or viral vector–based particles are depicted. An example of the viral vector–based particle is the bullet-shaped viral particle based on the rabies virus; part of the SARS-CoV-2 S1 protein and its native glycoprotein are displayed.IV, Examples of 3 live viral vector vaccines based on adenovirus, measles virus, and vesicular stomatitis virus (left to right). B, Structure of the Omicron S protein with mutations highlighted. The 7T9J structure was used to illustrate mutations in the Delta, Omicron BA.1, and Omicron BA.2 variants. Two monomers are shown as surface topology with the third, highlighting mutations, displayed as a ribbon. S1 domains are displayed as light blue, gray, and green, whereas S2 domains are shown in dark blue, gray, and green. The Delta and Omicron BA.1 variants are compared with one another (top panel), and the Omicron BA.1 and Omicron BA.2 variants are compared with one another (bottom panel). Mutations that are unique (relative to the variant with which it is being compared) to the Delta, Omicron BA.1 and Omicron BA.2 variants, are shown as yellow, red, and blue, respectively (depicted as spheres overlaid on the ribbon). Mutations present in both the Delta and Omicron BA.1 variants are depicted in orange, whereas those common to the Omicron BA.1 and Omicron BA.2 variants are shown in purple. A list of the mutations used in generating this figure can be accessed in Table E2 (available in the Online Repository at www.jacionline.org).