Omicron Variant: What You Need to Know

Jan 6, 2022

Omicron in the United States
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.

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.

Infections with the recently identified Omicron variant of SARS-CoV-2, the virus that causes COVID-19, are exponentially
increasing in multiple countries. Increases in infections are most likely due to a combination of two factors: increased
transmissibility and the ability of the variant to evade immunity conferred by past infection or vaccination (i.e., immune evasion).
Though the precise contribution of each of the two factors remains unknown, a substantial degree of immune evasion is likely as
has been demonstrated in early in vitro studies.
CDC has collaborated with partners to model scenarios of the epidemic trajectory in the U.S. that simultaneously consider
transmissibility and immune evasion. Results from scenario analyses indicate that current increases in Omicron cases are likely
to lead to a national surge in the coming weeks with peak daily numbers of new infections that could exceed previous peaks;
these scenarios may be realized as soon as January. In scenarios with lower immune evasion, a surge is still likely, but the peak
could be lower and begin as late as April 2022. Projected large surges in cases indicate surges of hospital demand even if severity
is reduced, because of the large number of anticipated cases occurring in a short period of time.

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.

Tests can tell you if you are currently infected with COVID-19.