To Cite this Publication:
Shayesteh, R. (2022). A review and comparison of two currently developed vaccines against SARS-CoV-2. In Davidson, P., & Amir, L. (Series Eds.). Covid-19-related assessments for Grade 12 Biology. Retrieved Month Date, Year, from https://www.researchgate.net/project/Covid19-related-assessment-for-Grade-12-Biology
A Review and Comparison of Two Currently Developed Vaccines Against SARS-CoV-2
SBI4U
Dr. Paul Davidson
30/4/2021
Kaur, S. P., & Gupta, V. (2020). COVID-19 Vaccine: A comprehensive status report. Virus Research, 288, 198114. https://doi.org/10.1016/j.virusres.2020.198114
This paper is a review of other journal findings.
I hereby confirm that this is my original work
Introduction
As of writing, a novel coronavirus has infected more than 150 million people worldwide, leaving more than 3 million individuals dead (John Hopkins University, 2021). The Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) is a zoonotic virus that has crossed the species barrier from an unknown animal to humans. It belongs to the category of beta coronaviruses of the subfamily Coronavirinae (Ou et al., 2020). Since the initial outbreak more than a year ago, the global scientific community has been working on potential treatments and vaccines. While SARS-CoV-2 has a 79% genetic sequence similarity to SARS-CoV, another virus from the same genus that caused an epidemic almost two decades ago, immunization from the latter will not guarantee safety from the former (Ou et al., 2020; Wu et al., 2020). The primary aim of all the developed vaccines is to build immunization against the viral mechanism of the new novel strain of the virus.
SARS-CoV-2 is a single-stranded RNA (ssRNA) virus, which is enveloped by a nucleocapsid (N) protein (Wu et al., 2020). The RNA contains at least 10 Open Reading Frames (ORFs) (Yoshimoto, 2020). ORFs consist of grouped codons, and each codon contains three nucleotides. Each codon of a messenger-RNA (mRNA) codes for a specific amino acid for the transfer-RNA (tRNA) to add to the growing polypeptide chain during the translation process (Campbell et al., 2020, p.390). Therefore, the ORFs contain the instructions to produce all the structural proteins (N, S, M, E) and the non-structural proteins (NSPs). The NSPs carry out crucial functions for viral infections, such as RNA replication (Yoshimoto, 2020). The E and M structural proteins are involved heavily in viral replication and carry out functions such as assembly and release (Wu et al., 2020). The S protein is responsible for viral attachment and host cell entry, making it a prime target for vaccine developers (Wrapp et al., 2020). The transmembrane S protein’s Receptor Binding Domain (RBD) attaches to the human Angiotensin-Converting Enzyme 2 (hACE2) receptors to facilitate entry into the target cells (Ou et al., 2020). Therefore, the objective of all the vaccines is to trigger the body’s immune response to produce S protein neutralizing antibodies to prevent infection.
Vaccines
The ChAdOx1 vaccine, more commonly referred to as the Oxford/AstraZeneca vaccine, utilizes viral vector technology to trigger an immune response. In this type of vaccine, a different harmless virus (the vector) is used as a transport method for the genetic instructions of the viral virus. The Oxford/Astrazeneca vaccine uses a synthesized adenovirus to deliver a section of the genetic material from SARS-CoV-2 to human cells. Specifically, the codons in the virus RNA that code for the spike protein were inserted into the E1 locus of the adenovirus DNA. The injected virus will bring the gene for the spike proteins to the cell's nucleus, where they can be transcribed and translated to produce the S proteins. While the infected cells will be destroyed by T cells, B cells will produce antibodies for the S proteins, which will help the body prevent infection when exposed to the SARS-CoV-2 virus (Van Doremalen et al., 2020). The results from randomized controlled phase 3 trials demonstrated an overall 70.4% efficacy for the Oxford/AstraZeneca vaccine (Voysey et al., 2020).
The BNT162ba vaccine, more commonly referred to as the Pfizer/BioNTech vaccine, utilizes mRNA technology to create immunization against SARS-CoV-2. In this type of vaccine, an mRNA strand that contains the codons that code for the RBD of the S protein is used to trigger an immune response. Since mRNA strands are fragile and will be broken apart by body cells upon entry, the strand is encapsulated in lipid nanoparticles to increase the stability of the vaccine. Once in a cell, the mRNA strand will act as a template to produce the Spike proteins. Similar to viral vector proteins, immune system cells will produce antibodies that will help prevent infection in the future (Mulligan et al., 2020). In phase 3 randomized controlled clinical trials, the Pfizer/BioNTech vaccine has demonstrated an overall 95% efficacy against Covid-19 infections (Polack et al., 2020).
Conclusion
For the Pfizer-BioNTech vaccine, more than 40000 individuals were involved in phase 3 randomized controlled trials. Half of the participants were given placebo shots, and the other half received the vaccine doses. The trials expanded to six countries worldwide, but the overwhelming majority of the participants were in the United States, with other participants from Argentina, Brazil, South Africa, Germany, and Turkey. All demographic groups were adequately present in the participant population; 49% were women, 58% were in the age range of 16 to 55, 35% were obese according to body mass index, and 21% had pre-existing health conditions. The wide range of participants ensures reliable data based on any demographic factors (Polack et al., 2020). In the phase 3 trials for the Oxford/AstraZeneca vaccine, more than 23000 individuals were involved across four different trials. The initial efficacy data only involved participants from two trials that met the inclusion requirements. Out of the 11000 people included, half received a placebo, and the other half received two doses of the vaccine. The data represents individuals from trials conducted in the UK and Brazil. However, a majority of the included participants are from the UK. The participants are less diverse for the Oxford/AstraZeneca vaccine trials; 65% are female, and 12% are 56 years old or older (Voysey et al., 2020). While the two vaccines have a considerable difference in reported efficacy, they cannot be accurately compared to each other as the conditions of their trials were different. For instance, the Oxford/AstraZeneca vaccine trials were conducted mostly in the UK, where a new viral variant with mutations in the Spike protein has spread across the country. On the other hand, the Pfizer/BionTech vaccine trials were mostly conducted in the US, where the new variant was not commonplace for the duration of the phase 3 trials.
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