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Understanding Omicron and Other COVID-19 Variants

This information was accurate at the time of publication. Due to the changing nature of the COVID-19 pandemic, some information may have changed since the original publication date.

Different versions, or variants, of the virus that causes COVID-19 (SARS-CoV-2) continue to emerge 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 post-doctoral research associate in the Department of Human Genetics at University of Utah, shares information about what is currently known.

How Variants from Viruses Emerge

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.

Types of COVID-19 Variants

New variants of COVID-19 continue to emerge. Some have evolved to be more transmissible while others have caused more severe illness. That's because the virus continues to change over time as it infects more people. Vaccination against COVID-19 continues to be the best way to protect yourself from severe illness, hospitalization, and death. COVID-19 vaccine booster shots substantially enhance protection.

BA.5 variant:

  • Identified as a variant of concern by the World Health Organization (WHO) in July 2022.
  • Is an Omicron sub-lineage.
  • Spreads more easily than previous variants.
  • Breakthrough infections are more common, even in people who were recently vaccinated or were infected by the virus. These people tend to have less severe illness.

Omicron variant:

  • Identified as a variant of concern by the WHO on November 26, 2021.
  • The variant was first detected in South Africa.
  • The Omicron variant has a large number of mutations and is more transmissible than Delta.
  • There's an increased risk of reinfection or breakthrough infections.
  • Omicron is less likely to cause severe illness than Delta.
  • The Omicron variant has a number of lineages and sub-lineages, with the three most common being BA.2, BA.4, and BA.5.

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.
  • 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.
  • 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.

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.