A variant is when a virus mutates slightly, or changes. Variants frequently happen in viruses, but sometimes a variant can make the virus spread more easily, can make symptoms worse (or better) or reduce the effectiveness of treatments and vaccines. The original COVID-19 virus has had many variants since it was first discovered, with some being labelled by the World Health Organization (WHO) as a ‘variant of concern’. A variant of concern is one that may change how the pandemic behaves, so the WHO pays close attention to it. These variants (named after letters of the Greek alphabet) include Alpha, Beta, Gamma, Delta and most recently Omicron.