Variants of Concern (VOCs) are specific strains of a virus that have mutations affecting their characteristics, such as transmissibility, severity, or vaccine effectiveness. These variants are monitored closely by health organizations like the World Health Organization to assess their potential impact on public health. When a variant is classified as a VOC, it means that it has shown evidence of spreading more easily or causing more severe illness compared to the original strain. Examples of VOCs include the Alpha, Beta, Gamma, and Delta variants of the SARS-CoV-2 virus, which causes COVID-19.