Important update: Healthcare facilities
CDC has updated select ways to operate healthcare systems effectively in response to COVID-19 vaccination. Learn more
UPDATE
Given new evidence on the B.1.617.2 (Delta) variant, CDC has updated the guidance for fully vaccinated people. CDC recommends universal indoor masking for all teachers, staff, students, and visitors to K-12 schools, regardless of vaccination status. Children should return to full-time in-person learning in the fall with layered prevention strategies in place.
UPDATE
The White House announced that vaccines will be required for international travelers coming into the United States, with an effective date of November 8, 2021. For purposes of entry into the United States, vaccines accepted will include FDA approved or authorized and WHO Emergency Use Listing vaccines. More information is available here.
UPDATE
Travel requirements to enter the United States are changing, starting November 8, 2021. More information is available here.

What You Need to Know About Variants

What You Need to Know About Variants

Omicron Variant

The Omicron Variant of Concern has been detected in the United States. CDC is following the details of this new variant. CDC’s Media Statement
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Information about Variants: Viruses constantly change through mutation and sometimes these mutations result in a new variant of the virus. Some variants emerge and disappear while others persist. New variants will continue to emerge. CDC and other public health organizations monitor all variants of the virus that causes COVID-19 in the United States and globally.

The Delta variant causes more infections and spreads faster than the original SARS-CoV-2 strain of the virus that cause COVID-19. Vaccines remain the best way to reduce your risk of severe illness, hospitalization, and death from COVID-19.

Top Things You Need to Know

  1. New variants of the virus are expected to occur. Taking measures to reduce the spread of infection, including getting a COVID-19 vaccine, are the best ways to slow the emergence of new variants.
  2. Vaccines reduce your risk of severe illness, hospitalization, and death from COVID-19.
  3. COVID-19 booster doses are recommended for individuals who are 18 years or older.
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Vaccines 

  • While vaccines reduce your risk of severe illness, hospitalization, and death from COVID-19, we don’t yet know how effective they will be against new variants that may arise, including Omicron.
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Symptoms 

  • All previous variants cause similar COVID-19 symptoms.
  • Some variants, such as the Alpha and Delta variants, may cause more severe illness and death.
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Masks 

  • Wearing a mask is an effective way to reduce the spread of earlier forms of the virus, the Delta variant and other known variants.
  • People who are not fully vaccinated should take steps to protect themselves, including wearing a mask indoors in public at all levels of community transmission.
  • People who are not fully vaccinated should take steps to protect themselves, including wearing a mask indoors in public at all levels of community transmission.
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Testing 

  • Tests used to detect COVID-19 may not tell you which variant you have.
  • As new variants emerge, scientists will continue to evaluate how well tests work to detect current infection.

Types of Variants

Scientists monitor all variants but may classify certain ones as  variants being monitored, variants of interest, variants of concern and variants of high consequence. Some variants spread more easily and quickly than other variants, which may lead to more cases of COVID-19. An increase in the number of cases will put more strain on healthcare resources, lead to more hospitalizations, and potentially more deaths.

These classifications are based on how easily the variant spreads, how severe the symptoms are, how the variant responds to treatments, and how well vaccines protect against the variant.

Variants of Concern

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Omicron - B.1.1.529

First identified: South Africa

Spread: May spread more easily than other variants, including Delta.

Severe illness and death: Due to the small number of cases, the current severity of illness and death associated with this variant is unclear.

Vaccine: Breakthrough infections in people who are fully vaccinated are expected, but vaccines are effective at preventing severe illness, hospitalizations, and death. Early evidence suggests that fully vaccinated people who become infected with the Omicron variant can spread the virus to others. All FDA-approved or authorized vaccines are expected to be effective against severe illness, hospitalizations, and deaths.  The recent emergence of the Omicron variant further emphasizes the importance of vaccination and boosters.

Treatments: Some monoclonal antibody treatments may not be as effective against infection with Omicron.

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Delta - B.1.617.2

First identified: India

Spread: Spreads more easily than other variants.

Severe illness and death: May cause more severe cases than the other variants

Vaccine: Breakthrough infections in people who are fully vaccinated are expected, but vaccines are effective at preventing severe illness, hospitalizations, and death. Early evidence suggests that fully vaccinated people who become infected with the Delta variant can spread the virus to others. All FDA-approved or authorized vaccines are effective against severe illness, hospitalization, and death.

Treatments: Nearly all variants circulating in the United States respond to treatment with FDA-authorized monoclonal antibody treatments.