The Omicron strain of the SARS-CoV-2 coronavirus and its variants

The SARS-CoV-2 coronavirus has been circulating among the world population for 3 years, infecting hundreds of millions of people. Numerous reports from all over the world indicate that the majority of infections are caused by the Omicron variant and its subvariants, which predominate over all the previously emerged variants. The genome of the Omicron strain has accumulated dozens of mutations that increase the virus’s adaptability and cause the emergence of new variants and subvariants with the increased contagiousness, transmissibility, and ability to evade the immune response. This compromises the protection provided by vaccines or the humoral immunity induced by previous infections. Although the biology of SARS-CoV-2 is well understood, its ability to infect, replicate, and spread in a population depends on the specific immune context during different periods of the pandemic. It is assumed that new variants arise as a result of chronic infection in immunocompromised individuals. The intralineage recombination is an opportunity for the virus to gain phenotypic advantages from distantly related circulating variants. The last of the subvariants of the Omicron variant, named «Kraken» due to its unprecedentedly high transmissibility, is a descendant of the recombinant line. The virus is constantly evolving in the direction of evading immune neutralization by vaccines, therefore, a constant work is underway to develop new, more effective vaccines and other antiviral agents.