Dec 01, 2021 10:00 AM

Author: University of Utah Health Communications

Different versions, or variants, of the virus that causes COVID-19 (SARS-CoV-2) are emerging around the world. Although it sounds alarming, viruses always change via mutation. As scientists work to learn more about these variants and how they may impact the United States, Stephen Goldstein, PhD, a postdoctoral research associate in the Department of Human Genetics at University of Utah, shares information about what is currently known. 

How Variants from Viruses Emerge

All viruses mutate

Every time a virus replicates, errors (mutations) occur in its genetic material. This is normal—and how variants arise. Usually, the changes either have no impact or are harmful to the virus. But once in a while, changes give the virus an advantage. This is what has happened with the SARS-CoV-2 variants of concern.

Scientists are studying these variants closely to determine whether they spread more easily. They are also investigating how effective today’s COVID-19 vaccines are against the variants and whether people who have already had COVID-19 or received a COVID-19 vaccine could become infected with the variants. So far, studies suggest that current vaccines work on these variants.

Types of COVID-19 Variants

Several variants of the SARS-CoV-2 virus have been identified around the world. The Centers for Disease Control and Prevention (CDC) have identified four variants of concern in the United States. Most recently, the World Health Organization (WHO) identified a new variant of concern, named Omicron. According to the organizations, these variants seem to spread more easily and quickly than other variants. Each variant arose independently, and all have unique mutations as well as mutations in common.

Omicron variant:

  • Identified as a variant of concern by WHO on November 26, 2021.
  • The variant was first detected in South Africa, which caused a surge in new COVID-19 infections. Omicron is now the dominant variant in many countries, including the U.S.
  • The Omicron variant has a large number of mutations and is more transmissible than Delta. There may also be an increased risk of reinfection or breakthrough infections. Like with other variants, COVID-19 vaccines help protect against severe illness, hospitalization, and death.
  • COVID-19 vaccine booster shots substantially enhance protection against Omicron.
  • Preliminary data shows that, while Omicron is more contagious, the length of exposure of infection seems to be shorter.
  • Emerging studies show that it appears that Omicron is less likely to cause severe illness than Delta. However, Omicron can still cause severe illness and hospitalization in some people, including in some young children.
  • Because Omicron is highly contagious, it is expected to infect a large number of people and may cause a surge in hospitalizations.

Delta variant:

  • First identified in December 2020 in India during a surge responsible for more than 30 million infections and at least 430,000 deaths.
  • The variant was first detected in the United States in March 2021 and is recognized as the dominant variant in the U.S. and globally.
  • It’s believed to be up to two times more transmissible than the Alpha variant (which was 50% more transmissible than the original, non-variant SARS-CoV-2).
  • Data shows the Delta variant is more contagious and transmissible than previous SARS-CoV-2 variants. It is unclear whether this variant causes more severe disease. Fully vaccinated people can get infected (breakthrough infections), but it occurs less often and symptoms are often less severe than in people who are unvaccinated.
  • New cases and hospitalization rates of COVID-19 infection significantly increased in the U.S. after a steady decline since January 2021.
  • One dose of a two-dose vaccine is only partially effective against this variant.
  • Full vaccination (achieved when it has been at least two weeks after the final dose of vaccine) remains highly effective against both symptomatic infection and severe disease/hospitalization.
  • Booster doses are now recommended for all adults six months after their second mRNA dose or two months after a J&J vaccination to maintain maximum protection against the Delta variant.

Gamma variant:

  • First emerged in Brazil in November 2020 and was detected in the United States at the end of January 2021.
  • It shares some critical mutations with Beta.
  • Is more susceptible to antibodies than Beta.
  • Spreads more quickly than the original, non-variant SARS-CoV-2.
  • Remains rare in the United States, though cases have increased steadily. 

Beta variant:

  • Emerged independently in South Africa in December 2020 and was detected in the United States in January 2021.
  • Spreads more quickly than non-variant SARS-CoV-2.
  • Most vaccines exhibit modest reduction in efficacy against this variant.
  • There is no evidence that it causes more severe illness or increases risk of death.
  • Very few cases of the variant have been found in the U.S.

 Alpha variant:

  • Emerged with a large number of mutations in the United Kingdom in September 2020 and was detected in the United States in December 2020.
  • The variant is about 50% more transmissible than the original SARS-CoV-2 virus and is associated with an increased risk of hospitalization and death.
  • New cases due to this variant are declining in the United States.

How Variants are Discovered

Variants are discovered by taking a swab from an infected patient, extracting genetic material from virus that is in the sample, and using sequencing equipment to read the genetic code. Genome sequencing is done around the world, including here in the U.S. This is how the spread of SARS-CoV-2 variants is monitored in communities and populations.

How to Protect Yourself Against COVID-19 Variants

The best way to avoid getting infected with new COVID-19 variants is to get vaccinated. While scientists continue to study vaccine efficacy on these variants, COVID-19 vaccines are considered to be the best method to protect yourself from preventing severe illness, hospitalization, and death from COVID-19.

With more transmissible variants emerging, it is important for all individuals to continue practicing interventions. This means following COVID-19 safety protocols such as wearing a face mask in public places, physical distancing, frequently washing your hands, and staying home when sick. Those who are fully vaccinated and aged 18 and older should get a COVID-19 booster shot.


Updated on January 6, 2022 to reflect new information on Omicron.

covid-19 coronavirus variant vaccine omicron delta

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