Inactivated SARS-CoV-2 Variant Zeta, Lineage P2_2021 (NY-Wadsworth-21006055-01/2021)

SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2) is the virus that caused the COVID-19 outbreak in Wuhan, China, in late 2019. As a member of the coronavirus family, it is characterized by its single-stranded RNA genome and spike protein (S protein), which facilitates entry into human cells by binding to the ACE2 receptor. The virus is primarily transmitted through respiratory droplets and aerosols, causing symptoms ranging from mild fever and cough to severe pneumonia, multi-organ failure, and even death, particularly in vulnerable populations. Over time, SARS-CoV-2 has undergone numerous mutations, resulting in the emergence of variants with altered transmissibility, virulence, or immune evasion properties. Organizations such as the World Health Organization classify these variants as variants of concern (VOC), variants of interest (VOI), and variants under surveillance (VUM), based on their epidemiological impact.

The Zeta variant, designated P.2 by the PANGO nomenclature, was first detected in Brazil in early 2021. A descendant of the B.1.1.28 lineage, Zeta shares some mutations with the more notorious Gamma variant (P.1) but lacks all of the concerning mutations. Key Zeta mutations include E484K in the spike protein, which has been associated with reduced neutralization by antibodies generated by prior infection or vaccination. This mutation has raised concerns about potential immune escape, although studies suggest that Zeta is less resistant to immunization than variants such as Beta (B.1.351) or Delta (B.1.617.2). The variant also carries other minor mutations, such as N501Y and D614G, that may enhance binding affinity and viral fitness.