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.
CDC is monitoring the current surge of COVID-19 cases. Learn more about the Omicron variant and its expected impact on hospitalizations.
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.
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.
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.
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.
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.
Vaccines remain the best public health measure to protect people from COVID-19, slow transmission, and reduce the likelihood of new variants emerging.
Masks offer protection against all variants.
Tests can tell you if you are currently infected with COVID-19.
Until we know more about the risk of Omicron, it is important to use all tools available to protect yourself and others.
CDC scientists are working with partners to gather data and virus samples that can be studied to answer important questions about the Omicron variant. Scientific experiments have already started. CDC will provide updates as soon as possible.
In the United States, CDC uses genomic surveillance to track variants of SARS-CoV-2, the virus that causes COVID-19 to more quickly identify and act upon these findings to best protect the public’s health. CDC established multiple ways to connect and share genomic sequence data being produced by CDC, public health laboratories, and commercial diagnostic laboratories within publicly accessible databases maintained by the National Center for Biotechnology Informationexternal icon (NCBI) and the Global Initiative on Sharing Avian Influenza Dataexternal icon (GISAID). If a variant is circulating at 0.1% frequency, there is a >99% chance that it will be detected in CDC’s national genomic surveillance.
microscope light icon
Science Brief: Omicron (B.1.1.529) Variant
On November 24, 2021, South Africa reported the identification of a new SARS-CoV-2 variant, B.1.1.529, to the World Health Organization (WHO). B.1.1.529 was first detected in specimens collected on November 11, 2021 in Botswana and on November 14, 2021 in South Africa.
CDC has been using genomic surveillance throughout the course of the pandemic to track variants of SARS-CoV-2, the virus that causes COVID-19, and inform public health practice.