Coronavirus disease 2019 (COVID-19) is a global pandemic started in Wuhan, China, in December 2019, resulting in huge economic and social consequences globally. Numerous variants of SARS-COV-2 virus are being tracked in the United States (US) and globally during this pandemic. Variants of Concern (VOCs) include B.1.1.7 (Alpha), B.1.351 (Beta), P.1 (Gamma), and B.1.617.2 (Delta). These variants are characterized by genetic mutations of the spike protein
(S protein) of the virus. These mutations can minimize the neutralization activity of antibodies by post vaccination sera and consequently affecting the immune response of the body against the virus. With this rapid rate of variants emergence, a lot of studies and updated reports were published to document the ongoing changes of the virus circulation and to study the effectiveness of available vaccines on these variants. This review showed that the currently available vaccines are of acceptable effectiveness against all possible clinical outcomes of COVID-19 infection caused by the VOCs, even delta variant. So full immunization with at least two doses is still highly recommended for all indicated groups of population to ensure acceptable protection against symptomatic disease, hospitalization and deaths.