The COVID-19 virus changes over time. This is normal and a part of how most viruses spread and cause disease. The different versions of the virus are called variants. Variants can change in ways that make them better at infecting people or worse at infecting them. They can also change in ways that help them avoid being detected by the immune system or vaccines.
During the pandemic, many different variants of the virus have emerged and dominated at times. Each time a new variant emerges, the World Health Organization gives it a name based on letters of the Greek alphabet. Examples include Alpha, Delta, and Omicron.
Variants can be tracked by their lineage or sublineage. Lineage refers to the group of variants that share an ancestor; for example, all the subvariants of Omicron are part of the same lineage. When two variants combine, forming a single, different lineage, they are said to be “recombinant.”
As COVID-19 continues to spread and infect more people, more of these variants will be identified. Some will fade away, while others may continue to spread. CDC will continue to update the public about COVID-19 variants on this page and through GISAID.
The COVID-19 vaccine is designed to protect against the most common variants. Vaccination lowers your risk of severe symptoms, hospitalization and death from the current Omicron strain of the virus. Vaccination remains important, even as the virus changes and the most common COVID-19 variants may decline in prevalence.