Neda Sinaei - Department of Biotechnology, Iranian Research Organization for Science and Technology, Tehran, Iran
Hamed Hekmatnezhad - Department of Basic Sciences, Sari Agricultural Sciences and Natural Resources University, Sari, Iran
Nafise Dani - Department of Biology, Science and Research Branch, Islamic Azad University, Tehran, Iran
Mona Keivan - Student Research Committee, School of Medical, Kermanshah University of Medical Sciences, Kermanshah, Iran

The new variant of severe acute respiratory syndrome coronavirus ۲ (SARS-CoV-۲) has once again sounded the alarm on healthcare systems worldwide and has caused concern in some countries. This variant has been identified in South Africa and initially called B.۱.۱.۵۲۹ and later renamed Omicron by the WHO. The transmissibility and immune evasion in the Omicron variant (B.۱.۱.۵۲۹) is higher than the previous variants. Compared to the previous dominant variant, which was called the Delta variant, the Omicron variant has a very high transmission power but luckily, Omicron's symptoms are less serious. According to the WHO, the Omicron variant has the potential to re-infect people who already have other variants of SARS-CoV-۲. Omicron contains at least ۳۲ mutations in the spike protein also other proteins that are required for viral replication and it is twice the size of delta variant. Half of the mutations in this variant occur in the area of the virus through which they bind to the cells of the human body and cause infection. The Omicron variant likely developed in one person during chronic infection with an immune system deficiency (possibly untreated HIV/AIDS). It is possible that injecting a booster dose of existing vaccines and subsequently increasing antibody levels will provide adequate protection and an appropriate barrier against Omicron. The purpose of this article is to evaluate the Omicron variant and compare it with other SARS-CoV-۲ variants and the effect of a booster dose in preventing disease progression.

SARS-CoV-۲, Omicron, B.۱.۱.۵۲۹, COVID-۱۹, Vaccines