1 For SARS-CoV-2, the mutation rate was approximately two mutations per month, and variants with clinical implication were not considered to be able to emerge at such a slow rate within a short period 2 however, chronic viral shedding in the setting of immunocompromised hosts produced viruses with multiple mutations, including in the S protein. In particular, an amino acid mutation of D480 A/G within the receptor binding domain (RBD) of the Spike (S) protein of SARS-CoV-1, which had the ability to escape from neutralizing antibodies, became the dominant variant as the outbreak proceeded.
Although the rate of evolution of coronavirus is slower compared to other RNA viruses, such as HIV-1 or influenza virus, antigenic drift occurred during the SARS-CoV-1 outbreak in 2003. Here, we review the molecular features, epidemiology, impact on transmissibility, disease severity, and vaccine effectiveness of VOCs.Īll viruses, including severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), evolve over time.
Current measures to reduce transmission as well as efforts to monitor and understand the impact of variants should be continued. VOCs can also impact the effectiveness of mRNA and adenovirus vector vaccines, although the currently authorized COVID-19 vaccines are still effective in preventing infection and severe disease. Given their ability to evade immune responses, VOC are less susceptible to monoclonal antibody treatments. In addition, VOCs exhibit decreased susceptibility to vaccine-induced and infection-induced immune responses, and thus possess the ability to reinfect previously infected and recovered individuals. VOCs have increased transmissibility compared to the original virus, and have the potential for increasing disease severity. As of September 15, 2021, there are four SARS-CoV-2 lineages designated as the VOC (alpha, beta, gamma, and delta variants). These variants are categorized as the variant of interest (VOI), variant of concern (VOC), and variant under monitoring (VUM). Since the COVID-19 pandemic first began in December 2019, the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus has continuously evolved with many variants emerging across the world.