CDC is working with state and local public health officials to monitor the spread of Omicron. As of December 20, 2021, Omicron has been detected in most states and territories and is rapidly increasing the proportion of COVID-19 cases it is causing. 

Omicron Data and Potential Spread: CDC is expecting a surge of COVID-19 cases in the coming days to weeks. Learn more about Omicron variant surveillance and potential rapid spread. 

What We Know about Omicron: CDC has been collaborating with global public health and industry partners to learn about Omicron, as we continue to monitor its course. We don’t yet know how easily it spreads, the severity of illness it causes, or how well available vaccines and medications work against it. 

Spread: The Omicron variant likely will spread more easily than the original SARS-CoV-2 virus and how easily Omicron spreads compared to Delta remains unknown. CDC expects that anyone with Omicron infection can spread the virus to others, even if they are vaccinated or don’t have symptoms. 

Severe Illness: More data are needed to know if Omicron infections, and especially reinfections and breakthrough infections in people who are fully vaccinated, cause more severe illness or death than infection with other variants. 

Vaccines: Current vaccines are expected to protect against severe illness, hospitalizations, and deaths due to infection with the Omicron variant. However, breakthrough infections in people who are fully vaccinated are likely to occur. With other variants, like Delta, vaccines have remained effective at preventing severe illness, hospitalizations, and death. The recent emergence of Omicron further emphasizes the importance of vaccination and boosters. 

Treatments: Scientists are working to determine how well existing treatments for COVID-19 work. Based on the changed genetic make-up of Omicron, some treatments are likely to remain effective while others may be less effective.