Omicron is a variant of the SARS-CoV-2 virus, which causes COVID-19. First identified in late 2021, it has a high number of mutations in its spike protein, leading to increased transmissibility compared to earlier variants. This has raised concerns about its potential to spread rapidly in populations. Despite its ability to spread quickly, studies have shown that Omicron generally causes milder illness than previous variants, especially in vaccinated individuals. Vaccines remain effective in reducing severe disease and hospitalization, although breakthrough infections can occur. Public health measures continue to be important in managing its spread.