Inactivated SARS-CoV-2 Variant Omicron, Lineage BF.7 (USA/NY-Wadsworth-22042128-01/2022)

The SARS-CoV-2 Omicron variant (B.1.1.529), first discovered in November 2021, marked a major turning point in the COVID-19 pandemic due to its unprecedented transmissibility and immune evasion capabilities. Characterized by an unusually high number of mutations, particularly in the spike protein, the Omicron variant rapidly surpassed previous variants, such as the Delta variant, leading to a surge in global infections. Analysis of the Omicron variant''s genomic sequence revealed a large number of non-synonymous mutations, including multiple mutations in the spike protein, which have been linked to transmissibility, disease severity, and immune evasion. Overall, over 60 substitutions/deletions/insertions have been identified in the Omicron variant, making it the most mutated of all identified SARS-CoV-2 variants to date. In ORF1a, the Omicron variant contains six substitutions (K856R, L2084I, A2710T, T3255I, P3395H, and I3758V) and two deletions totaling four amino acids (amino acid 2083 and amino acids 3674-3676). In ORF1b, the variant contains two substitutions (P314L and I1566V). Additionally, a P10S substitution at positions 27-29 and a three-residue deletion were observed in ORF9b. Regarding structural proteins, there is one substitution (T9I) in the envelope protein (E), three substitutions (D3G, Q19E, and A63T) in the membrane protein (M), and three substitutions and a three-residue deletion in the nucleocapsid protein (N).

A notable Omicron substrain is BF.7 (BA.5.2.1.7), a descendant of the BA.5 variant. BF.7 attracted attention in late 2022 for its rapid spread, particularly in regions such as China, where it triggered significant waves of infection. This substrain carries key mutations, including the R346T mutation in the spike protein, which enhances immune evasion by reducing antibody neutralization. Studies have shown that BF.7 is approximately 10-20% more transmissible than its parent strain, BA.5, but its severity appears comparable to other Omicron strains. Despite its competitive advantage, BF.7 was ultimately replaced by newer variants such as XBB.1.5, highlighting the dynamic nature of viral evolution. Ongoing surveillance remains critical to monitoring the adaptability and impact of emerging SARS-CoV-2 strains.