The challenges of COVID-19 Delta variant: Prevention and vaccine development

Several SARS-CoV-2 variants have emerged since the pandemic, bringing about a renewed threat to the public. Delta variant (B.1.617.2) was first detected in October 2020 in India and was characterized as variants of concern (VOC) by WHO on May 11, 2021. Delta variant rapidly outcompeted other variants to become the dominant circulating lineages due to its clear competitive advantage. There is emerging evidence of enhanced transmissibility and reduced vaccine effectiveness (VE) against Delta variant. Therefore, it is crucial to understand the features and phenotypic effects of this variant. Herein, we comprehensively described the evaluation and features of Delta variant, summarized the effects of mutations in spike on the infectivity, transmission ability, immune evasion, and provided a perspective on efficient approaches for preventing and overcoming COVID-19.