Abstract
Simple SummaryThe coronavirus disease 2019 (COVID-19) pandemic, caused by the novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), was first encountered in December of 2019 in Wuhan, China. As of now, there have been over 200 million infections and 4 million deaths attributed to the virus. Due to this, it has been a priority to find an effective preventative measure, and numerous vaccines have been developed. Although the developed vaccines share the target of blocking viral entry by the spike protein, their pharmacology and efficacy differs. As such, the mechanism of action and the elicited immune response of the most common COVID-19 vaccines have been compared to help determine which vaccine is most efficacious and is best suited to prevent reinfection and address viral mutations.It has been over a year since SARS-CoV-2 was first reported in December of 2019 in Wuhan, China. To curb the spread of the virus, many therapies and cures have been tested and developed, most notably mRNA and DNA vaccines. Federal health agencies (CDC, FDA) have approved emergency usage of these S gene-based vaccines with the intention of minimizing any further loss of lives and infections. It is crucial to assess which vaccines are the most efficacious by examining their effects on the immune system, and by providing considerations for new technological vaccine strategies in the future. This paper provides an overview of the current SARS-CoV-2 vaccines with their mechanisms of action, current technologies utilized in manufacturing of the vaccines, and limitations in this new field with emerging data. Although the most popular COVID-19 vaccines have been proven effective, time will be the main factor in dictating which vaccine will be able to best address mutations and future infection.
Highlights
The first outbreak of the COVID-19 infection occurred in Wuhan, China in 2019 where many patients had symptoms that were similar to respiratory infections and this infection rapidly spread [1]
Clinical trials for the Johnson & Johnson (J&J) vaccine began in June of 2020, and the phase III trials had more than 43,000 ethnically diverse participants; this vaccine was determined to be 66% effective [86]. All these viral vector vaccines are unable to replicate, which is explained by the fact that certain genes that are essential for replication were deleted and exchanged by genes that code for the COVID-19 spike protein [83]
Once the mRNA vaccine is injected, the positively charged lipid nanoparticle is attracted to the endosomes and this interaction starts the process of receptormediated endocytosis, which triggers the SLN to degrade and release the mRNA (Figure 2)
Summary
The first outbreak of the COVID-19 infection occurred in Wuhan, China in 2019 where many patients had symptoms that were similar to respiratory infections and this infection rapidly spread [1]. The COVID-19 pandemic has catastrophically swept across the world, resulting in over 200 million infections and 4.5 million deaths (as of 30 August 2021) [2]. The current variants that are of concern which have characteristics of increased transmissibility and increased virulence include the Alpha, Beta, Gamma, and Delta variants [10]. Coronaviruses are known to infect many animals, have the largest RNA genome and contain four subfamilies which include alpha, beta, gamma, and delta coronaviruses [11]. All four subfamilies have the commonality of being from a zoonotic origin where the alpha and beta coronaviruses emerge from bats and the gamma and delta coronaviruses emerge from birds [11]. The most recent occurrences of coronavirus infections occurred in 2001 and 2012 with both being from zoonotic origins. The important envelope proteins include the spike (S) protein, envelope (E) protein, and the membrane (M) protein, which mediates viral entry into the host cell [13]
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