Why the new variant of COVID-19 - Omicron is a cause of concern? What does it mean that this variant has many mutations? Dr Julian W Tang, Clinical Virologist, University of Leicester says, "When mutations happen, there changes in the shape on the S protein because of which the antibodies are not able to combine well with the virus and that reduces the protection against the virus for those variants." He further said that one has to update the vaccine so that it can combine well enough to reduce severity and death.