According to the CDC, the Delta variant (B.1.617.2) is now the dominant variant in the United States, accounting for 99% of new COVID-19 cases (as of Sept. 25.) 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. 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.