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SARS-CoV-2, the virus that causes COVID-19, has mutated many times since it first broke out in late 2019. Those mutations have caused different variants of COVID-19 to appear around the world.
It is common for viruses to mutate. Some disease variants are more concerning than others. They may be more transmissible or cause more severe illness, or approved treatments or vaccines may be less effective against them.
One variant of concern circulating globally right now is the Delta variant (B.1.617.2). The variant is now in dozens of countries around the world, including the United States.
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What Is the Delta Variant?
The Delta variant first emerged in late 2020. It has since spread around the world and has become the dominant variant of COVID-19 in many countries.
According to Centers for Disease Control and Prevention (CDC) data, the Delta variant caused 9.5% of new U.S. COVID-19 cases in the 2-week period that ended June 5.
CDC Director Rochelle Walensky, MD, MPH, said the Delta variant could become the dominant variant of COVID-19 in the U.S.
The CDC classifies the Delta variant as a variant of concern (VOC). According to the CDC, variants of concern may:
- Be more transmissible.
- Cause more severe disease.
- Be less susceptible to existing treatments and vaccines.
- Interfere with diagnostic test targets.
Is the Delta variant more contagious?
Reported data show the Delta variant is more transmissible. According to Public Health England, the Delta variant has a 60% higher risk of transmission compared to the Alpha (B.1.1.7) variant, a variant of concern that is now widespread in the U.S.
A mutation of the Delta variant known as Delta Plus (B.1.617.2.1) may also be a concern. Delta Plus may be more transmissible and cause bigger health problems, according to health officials in India. However, more data is needed about Delta Plus.
Scientists continue to study the Delta and other variants to determine their risk of transmission.
Does the Delta variant make you sicker?
In addition to being more transmissible, the Delta variant appears to cause more severe illness.
Public Health England released a report on the risk of hospitalization from the Delta variant. According to the report, the risk of hospitalization from the Delta variant is 2.61 times higher than the Alpha variant.
A study in The Lancet reported the hospitalization risk from the Delta variant was more than 2 times higher than the Alpha variant.
Scientists continue to study the Delta variant and others to determine the risk of severe illness, hospitalization, and death.
Do COVID-19 vaccines work against the Delta variant?
The U.S. Food and Drug Administration (FDA) has authorized or approved COVID-19 vaccines developed by Pfizer-BioNTech, Moderna, and Johnson & Johnson/Janssen (J&J).
The vaccines are highly effective against Delta, the CDC says, especially in preventing severe outcomes.
The CDC says the Delta variant may have an impact on the effectiveness of some authorized monoclonal antibody treatments. However, more data is needed to see how effective monoclonal antibodies are against the variant.
Scientists continue to study how Delta and other COVID-19 variants affect vaccines and other treatments.
How to Protect Against the Delta Variant
The best way to reduce your risk from the Delta variant is to get vaccinated. Currently, all Americans 5 and older are eligible for the COVID-19 vaccine.
The authorized vaccines are highly effective against COVID-19, especially in preventing severe illness, hospitalization, and death.
It is possible to get COVID-19 even after getting vaccinated. But unvaccinated people are at greater risk of infection and severe outcomes.
To schedule a vaccine appointment at UPMC, visit Vaccine.UPMC.com. Or call 844-876-2822 between 8 a.m. and 5 p.m., Monday through Friday.
If you are not fully vaccinated, continue to follow other COVID-19 preventive efforts. These include wearing a facemask and physically distancing in public.
For more information about COVID-19, visit UPMC.com/COVID19.
Editor's Note: This article was originally published on , and was last reviewed on .
Centers for Disease Control and Prevention, COVID Data Tracker, Variant Proportions. Link
Centers for Disease Control and Prevention, SARS-CoV-2 Variant Classifications and Definitions. Link
The Guardian, India COVID Variant May Increase Risk of Hospital Admission, Early Data Suggests. Link
Michael E. Miller, Jennifer Hassan, Lateshia Beachum, and Hannah Knowles, The Washington Post, Delta variant Could Become Dominant Strain in U.S. This Summer, CDC Head Says. Link
Public Health England, Vaccines Highly Effective Against Hospitalisation from Delta Variant. Link
Aziz Sheikh, Jim McMenamin, Bob Taylor, Chris Robertson, The Lancet, SARS-CoV-2 Delta VOC in Scotland: Demographics, Risk of Hospital Admission, and Vaccine Effectiveness. Link
Arshard R. Zargar, CBS News, Delta Plus: As U.S. Grapples with Delta Variant, India Raises Alarm over a New COVID Strain Mutated from It. Link
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