The current COVID-19 pandemic, caused by severe acute respiratory syndrome-coronavirus 2 (SARS-CoV-2), has raised significant economic, social, and psychological concerns. The rapid spread of the virus, coupled with the absence of vaccines and antiviral treatments for SARS-CoV-2, has galvanized a major global endeavor to develop effective vaccines. Within a matter of just a few months of the initial outbreak, research teams worldwide, adopting a range of different strategies, embarked on a quest to develop effective vaccine that could be effectively used to suppress this virulent pathogen. In this review, we describe conventional approaches to vaccine development, including strategies employing proteins, peptides, and attenuated or inactivated pathogens in combination with adjuvants (including genetic adjuvants). We also present details of the novel strategies that were adopted by different research groups to successfully transfer recombinantly expressed antigens while using viral vectors (adenoviral and retroviral) and non-viral delivery systems, and how recently developed methods have been applied in order to produce vaccines that are based on mRNA, self-amplifying RNA (saRNA), and trans-amplifying RNA (taRNA). Moreover, we discuss the methods that are being used to enhance mRNA stability and protein production, the advantages and disadvantages of different methods, and the challenges that are encountered during the development of effective vaccines.

中文翻译：

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疫苗接种策略：传统疫苗方法与结合佐剂的新一代策略

当前由严重急性呼吸系统综合症冠状病毒 2 (SARS-CoV-2) 引起的 COVID-19 大流行引起了严重的经济、社会和心理问题。该病毒的迅速传播，加上缺乏针对 SARS-CoV-2 的疫苗和抗病毒治疗，激发了全球开发有效疫苗的重大努力。在最初爆发的短短几个月内，世界各地的研究团队采取了一系列不同的策略，着手开发可有效用于抑制这种剧毒病原体的有效疫苗。在这篇综述中，我们描述了疫苗开发的常规方法，包括将蛋白质、肽和减毒或灭活病原体与佐剂（包括基因佐剂）结合使用的策略。我们还详细介绍了不同研究小组在使用病毒载体（腺病毒和逆转录病毒）和非病毒递送系统时成功转移重组表达抗原所采用的新策略，以及如何应用最近开发的方法来生产疫苗它们基于 mRNA、自扩增 RNA (saRNA) 和反式扩增 RNA (taRNA)。此外，我们还讨论了用于增强 mRNA 稳定性和蛋白质产量的方法、不同方法的优缺点以及有效疫苗开发过程中遇到的挑战。以及如何应用最近开发的方法来生产基于 mRNA、自扩增 RNA (saRNA) 和反式扩增 RNA (taRNA) 的疫苗。此外，我们还讨论了用于增强 mRNA 稳定性和蛋白质产量的方法、不同方法的优缺点以及有效疫苗开发过程中遇到的挑战。以及如何应用最近开发的方法来生产基于 mRNA、自扩增 RNA (saRNA) 和反式扩增 RNA (taRNA) 的疫苗。此外，我们还讨论了用于增强 mRNA 稳定性和蛋白质产量的方法、不同方法的优缺点以及有效疫苗开发过程中遇到的挑战。