Articles: sars-cov-2.
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Omicron, the new Covid-19 variant, has already become dominant in many countries and is spreading at an unprecedented speed. The objective of this study was to review the existing literature on Omicron's transmissibility, immune evasion, reinfection, and severity. A literature search was performed using "PubMed," "Web of Science," "Scopus," "ScienceDirect," "Google Scholar," "medRxiv," and "bioRxiv." Data were extracted from articles that reported at least one of the following: transmissibility, immune evasion, reinfection, and severity related to Omicron. ⋯ Despite Omicron's higher potential to evade immunity, vaccines and booster shots were found to be still significantly effective in protecting against severe Covid-19 infections. Omicrons may be less severe than other variants of concern. However, its immune evasiveness and rapid spread pose an enormous threat to the global healthcare system.