Abstract
Severe Acute Respiratory Syndrome Coronavirus 2 is the causative agent of the current 2019 Coronavirus pandemic and its genome has constantly acquired mutations since it was first described at the end of 2019. On August 30, the World Health Organization named Mu (letter of the Greek alphabet) to the variant of interest B.1.621, identified for the first time in Colombia, joining lambda, another variant of interest, and five variants of concern: Alpha, Beta, Gamma, Delta and Omicron. The Mu variant exhibits genomic changes that affect virus transmissibility, disease severity, and resistance to vaccine-induced immune responses, as well as diagnostic evasion and drug susceptibility. This review describes the most important epidemiological and immunological aspects of the Mu variant: the main mechanisms of evasion of the immune response; the variation in the efficiency of the vaccines; and how some of the specific mutations may be responsible for these phenomena.
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