Abstract
The current study systematically reviewed, summarized and meta-analyzed the clinical features of the vaccines in clinical trials to provide a better estimate of their efficacy, side effects and immunogenicity. All relevant publications were systematically searched and collected from major databases up to 12 March 2021. A total of 25 RCTs (123 datasets), 58,889 cases that received the COVID-19 vaccine and 46,638 controls who received placebo were included in the meta-analysis. In total, mRNA-based and adenovirus-vectored COVID-19 vaccines had 94.6% (95% CI 0.936–0.954) and 80.2% (95% CI 0.56–0.93) efficacy in phase II/III RCTs, respectively. Efficacy of the adenovirus-vectored vaccine after the first (97.6%; 95% CI 0.939–0.997) and second (98.2%; 95% CI 0.980–0.984) doses was the highest against receptor-binding domain (RBD) antigen after 3 weeks of injections. The mRNA-based vaccines had the highest level of side effects reported except for diarrhea and arthralgia. Aluminum-adjuvanted vaccines had the lowest systemic and local side effects between vaccines’ adjuvant or without adjuvant, except for injection site redness. The adenovirus-vectored and mRNA-based vaccines for COVID-19 showed the highest efficacy after first and second doses, respectively. The mRNA-based vaccines had higher side effects. Remarkably few experienced extreme adverse effects and all stimulated robust immune responses.
Highlights
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a non-segmented positive-sense, single-stranded ribonucleic acid (RNA) beta coronavirus [1] that was first reported in Wuhan, China
Different strategies have been considered for the development of vaccines against SARS-CoV-2 based on the following vaccine platforms: (I) Nucleic acid mRNA-based vaccines are the newest generation of vaccine production approach [5]
The current vaccines developed by the companies Pfizer and Moderna utilize synthetic mRNA encoding the sequence of the coronavirus’s signature spike protein (S-protein) that is encapsulated within a lipid vesicle nanoparticle. (II) Viral vector vaccines that are developed with new biotechnology [6]
Summary
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a non-segmented positive-sense, single-stranded ribonucleic acid (RNA) beta coronavirus [1] that was first reported in Wuhan, China. Over 140 million infected and 3 million deaths are reported from COVID-19 by April 2021, with the death rate accelerating; according to WHO, the case fatality ratio (CFR) of SARS-CoV-2 ranges from less than 0.1% to over 25% depending on the country [2]. To overcome this pandemic, vaccination is the hope for a safe and effective way to help build protection and reduce disease spread [3]. A modified existing virus, able to infect human cells, is introduced carrying the genetic code of the target virus antigen in order to stimulate an immune response. GlaxoSmithKline and Medicago used a plant-derived platform to produce a particle that elicits neutralizing antibody and immune cell (e.g., TH1 T cell) responses against COVID-19
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