ABSTRACT
The novel 2019 Corona viruses are enveloped RNA genome virus, with a 79% genome similarity to the previous 2003 SARS Coronavirus-1 (SARS-CoV-1). Up to date the confirmed cases worldwide 11,327,790 And 209,509 in Saudi Arabia. The SARS-CoV-2 is a single strand RNA belongs to Beta corona virus. The phylogenetic analysis suspected that bats are the primary reservoir, however the zoonotic intermediate host that transfer SARS-CoV-2 to human is not identified. The glycoprotein spike exclusively on the SARS-CoVs-2 species binds to the host cell receptor through a region called receptor-binding domain (RBD) and mediates viral entry. SARS-CoV-2 targeting Angiotensin-converting enzyme 2 explain the reason behind the infection of the respiratory system especially. S glycoprotein is the most important protein of the virus while it is the best target for entry inhibitors, neutralizing antibody, and vaccine development. Besides the role of antibodies to eliminate virus separation, it can also reas viral entry in some virus species through a mechanism termed antibody-dependent enhancement (ADE) under certain conditions. This mechanism is the main block in the way of vaccine development against SARS-CoV 2. The balance between getting the induction of immunity protection and developing an enhanced susceptibility to virus infection after vaccination against SARS-CoV-2 is a highly sensitive and delicate approach and has a high risk. This novel version of the virus has many routes for infection, this may describe its ability to spread at a high rate and its high aggressivity compared to the previous one every year.