The COVID-19 pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) lasted from March 2020 to May 2023, infecting over 689 million and causing 6.9 million deaths globally. SARS-CoV-2 enters human cells via the spike protein binding to ACE2 receptors, leading to viral replication and an exaggerated immune response characterized by a “cytokine storm.” This review analyzes the COVID-19 pathogenesis, strains, risk factors for severe disease, and vaccine types and effectiveness. A systematic literature search for 2020–2023 was conducted. Results show the cytokine storm underlies COVID-19 pathogenesis, causing multiorgan damage. Key viral strains include Alpha, Beta, Gamma, Delta, and Omicron, differing in transmissibility, disease severity, and vaccine escape. Risk factors for severe COVID-19 include older age, obesity, and comorbidities. mRNA, viral vector, and inactivated vaccines effectively prevent hospitalization and death, although new variants exhibit some vaccine escape. Ongoing monitoring of emerging strains and vaccine effectiveness is warranted. This review provides updated information on COVID-19 pathogenesis, viral variants, risk factors, and vaccines to inform public health strategies for containment and treatment.

由严重急性呼吸综合征冠状病毒2（SARS-CoV-2）引起的COVID-19大流行从2020年3月持续到2023年5月，在全球范围内感染了超过6.89亿人，并造成690万人死亡。SARS-CoV-2 通过与 ACE2 受体结合的刺突蛋白进入人体细胞，导致病毒复制和以“细胞因子风暴”为特征的过度免疫反应。本综述分析了 COVID-19 的发病机制、毒株、严重疾病的危险因素以及疫苗类型和有效性。对 2020-2023 年进行了系统的文献检索。结果表明，细胞因子风暴是 COVID-19 发病机制的基础，可导致多器官损伤。主要病毒株包括 Alpha、Beta、Gamma、Delta 和 Omicron，它们在传播性、疾病严重程度和疫苗逃逸方面有所不同。严重 COVID-19 的危险因素包括年龄较大、肥胖和合并症。mRNA、病毒载体和灭活疫苗可以有效预防住院和死亡，尽管新变种表现出一些疫苗逃逸现象。有必要对新出现的毒株和疫苗的有效性进行持续监测。本综述提供了有关 COVID-19 发病机制、病毒变异、危险因素和疫苗的最新信息，为遏制和治疗的公共卫生策略提供信息。