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Is Omicron worse than Delta?

Medically reviewed by Melisa Puckey, BPharm. Last updated on Nov 28, 2023.

Does the Omicron Variant of COVID-19 worse than the Delta Variant?

Official answer


At this stage it is too early to know if Omicron (GR/484A or B.1.1.529), the new variant of the coronavirus that causes COVID-19, is more easily transmitted, causes more severe disease, or whether vaccine protect against illness, when compared to the Delta Variant.

What we do know is that on November 26, 2021 the World Health Organisation (WHO) classified Omicron as Variant of Concern (VOC). This means that they believe Omicron could be:

  • More easily transmitted or,
  • Cause more severe illness or change of usual symptoms or,
  • Change of how effective the public health and social measures, tests, vaccines, treatments are on the new strain.

What is a Variant of a Virus?

  • A variant of a virus is when there has been a change (mutation) in the virus’s genes.
  • This is the way viruses evolve and change over time.
  • Most changes are small and do not make any difference to how sick it makes you or how easy it is to pass on the viruses.
  • Sometimes a variant may be more easily transmitted or result in a more severe illness.
  • These mutations are monitored a lot more intensely, with the World Health Organisation classifying them as Variants of Interest (VOIs) and Variants of Concern (VOCs).
  • Other variants that the WHO have classified as Variants of Concern are Alpha, Beta, Gamma and Delta.

What do we know about Omicron?

  • Researchers studying genome-sequencing have reported that Omicron has 30 mutations on the spike protein which could affect how easily it is transmitted and how well your body's immune system can respond to it.
  • Omicron was detected in COVID-19 samples collected between 12 and 20 November 2021 in Gauteng in South Africa. The subsequent sudden increase in Omicron Covid-19 cases caused concern that it may be more transmissible than the Delta variant.
  • By November 28, 2021 it had been detected in USA, Botswana, South Africa, Australia, United Kingdom, Hong Kong, Italy, Belgium, Israel, Austria, Netherlands, Canada, Germany, Spain and Czech Republic.

Will COVID-19 tests be able to detect the Omicron Variant?

  • The way COVID-19 tests work is they look for specific viral proteins that are on the SARS-CoV-2 virus (the virus that causes COVID-19), if the proteins are there then the test is positive and if there is none of that specific protein, then the COVID-19 test will be negative.
  • Genetic variants of the SARS-CoV-2 virus may change the proteins that they have so that some proteins longer there. This means if the COVID-19 test being used on a SARS-CoV-2 variant is looking for that one specific protein and that protein isn’t there, then the COVID-19 test result will be negative, even though the person is COVID-19 positive. This is called a false negative.
  • Molecular tests that look for multiple genetic targets are less likely to give false negative results.

Related questions

Covid-19 Tests with reduced ability to detect the Omicron variant of the the SARS-CoV-2 virus

Tide Laboratories DTPM COVID-19 RT-PCR Test

  • The FDA updated information on Tide Laboratories DTPM COVID-19 RT-PCR Test on December 7, 2021.
  • This is a single target test which is not expected to detect the SARS-CoV-2 Omicron variant due to the nine-nucleotide deletion .
  • This test is still expected to work for other known SARS-CoV-2 variants

What more do we need to know about Omicron?

Researches will be looking at Omicron and comparing it against Delta to find out:

  • How easily is it transmitted?
  • How sick does it make people?
  • Do the current COVID-19 vaccines protect against illness?
  • Do other current COVID-19 tests detect Omicron variant infection?
  • Will current COVID-19 treatments work?

On the November 28, 2021 the WHO statement "Update on Omicron" confirmed that more information from studies is needed for the Omicron variant to better understand transmissibility, severity of illness, effectiveness of vaccines and tests, and current treatments.

Click here for information on: COVID-19: Treatments and Vaccines

Click here for information on: COVID-19: Symptoms, Prevention and Risks

  • Heavily mutated Omicron variant puts scientists on alert: [Accessed November 29, 2021]
  • World Health Organisation: Tracking SARS-CoV-2 Variants. [Accessed November 29, 2021]
  • GISAID: Community rapidly shares genomes of new variant of concern Omicron of the pandemic coronavirus: [Accessed November 29, 2021]
  • GISAID Tracking of Variants VOC Omicron GR/484A (B.1.1.529) [Accessed November 30, 2021]
  • Classification of Omicron (B.1.1.529): SARS-CoV-2 Variant of Concern: [Accessed November 30, 2021]
  • World Health Organisation Statement: Update on Omicron [Accessed November 30, 2021]
  • SARS-CoV-2 Viral Mutations: Impact on COVID-19 Tests [Accessed December 8, 2021]

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