Viruses constantly change through mutation, and new variants of a virus are expected to occur over time. The new COVID-19 variants are being studied to understand if they spread more easily, impact the severity of illness, how the infection is treated and how effective COVID-19 vaccines are. For example, the Delta variant causes more infections and spreads faster than earlier forms of the virus that causes COVID-19. The best way to slow the emergence of new variants is to reduce the spread of infection by taking measures to protect yourself, including getting a COVID-19 vaccine when available.