Authors: Karim SSA, de Oliveira T
Journal: NEJM, 2021. DOI: DOI: 10.1056/NEJMc2100362
Across the world, there are mul-tiple variants of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the virus that causes coronavirus disease 2019 (Covid-19). SARS-CoV-2 variants have been classified by the Centers for Disease Control and Prevention (CDC) as variants of interest, variants of concern, and variants of high consequence. Three new variants1 that have rapidly become dominant within their countries have aroused concerns: B.1.1.7 (also known as VOC-202012/01), 501Y.V2 (B.1.351), and P.1 (B.22.214.171.124).
The B.1.1.7 variant (23 mutations with 17 amino acid changes) was first described in the United Kingdom on December 14, 2020; the 501Y.V2 variant (23 mutations with 17 amino acid changes) was initially reported in South Africa on December 18, 2020; and the P.1 variant (approximately 35 mutations with 17 amino acid changes) was reported in Brazil on January 12, 2021. By February 22, 2021, the B.1.1.7 variant had been reported in 93 countries, the 501Y.V2 variant in 45, and the P.1 variant in 21.1 All three variants have the N501Y mutation, which chang-es the amino acid asparagine (N) to tyrosine (Y) at position 501 in the receptor-binding domain of the spike protein. The 501Y.V2 and P.1 vari-ants both have two additional receptor-binding–domain mutations, K417N/T and E484K. These mutations increase the binding affinity of the receptor-binding domain to the angiotensin-con-verting enzyme 2 (ACE2) receptor. Four key con-cerns stemming from the emergence of the new variants are their effects on viral transmissibility, disease severity, reinfection rates (i.e., escape from natural immunity), and vaccine effectiveness (i.e., escape from vaccine-induced immunity).