SARS-CoV-2 Omicron variant

a variant of SARS-CoV-2

The Omicron variant is a form of SARS-CoV-2, the virus that causes COVID-19. It was first reported to the World Health Organization (WHO) from South Africa on 24 November 2021.[1] On 26 November 2021, the WHO called it a variant of concern, and named it "Omicron". Omicron is a letter in the Greek alphabet.[2]

Confirmed cases of the Omircron variant worldwide
  100,000–999,999 Confirmed cases
  10,000–99,999 Confirmed cases
  1,000–9,999 Confirmed cases
  100–999 Confirmed cases
  10–99 Confirmed cases
  1–9 Confirmed cases
  No confirmed cases, no population, or no data available

Omicron multiplies around 70 times faster than the Delta variant in the bronchi, but it is less severe than other strains, especially the Delta variant.[3][4] Omicron might be less able to enter deep lung tissue.[5] Omicron infections are 91 percent less fatal than the delta variant, with 51 percent less risk of hospitalization.[6]

Vaccines can protect against severe disease and hospitalisation especially after a third dose of an mRNA vaccine is given.[7][8] Early data found that double vaccination give 30 to 40 percent protection against infection and around 70 percent protection against hospitalization. A recent third vaccine dose boosts effectiveness against infection to around 75 percent, and 88 percent for severe disease.[9]


  1. "Classification of Omicron (B.1.1.529): SARS-CoV-2 Variant of Concern". World Health Organization. 26 November 2021. Archived from the original on 26 November 2021. Retrieved 26 November 2021.
  2. Parekh, Marcus; Platt, Poppie; Team, Global Health Security; Barnes, Joe (26 November 2021). "Coronavirus latest news: EU suspends all flights to southern Africa over omicron Covid variant fears". The Telegraph. ISSN 0307-1235. Archived from the original on 26 November 2021. Retrieved 26 November 2021.
  3. Harvard Medical School (6 January 2022). "Coronavirus Resource Center - Harvard Health". Harvard Health Publishing. Archived from the original on 11 January 2022. Retrieved 7 January 2022. Lab studies, animal studies, and epidemiological data all indicate that Omicron may cause less severe disease than previous variants.
  4. David Leonhardt (5 January 2022). "Omicron Is Milder". The New York Times. Retrieved 7 January 2022. A few weeks ago, many experts and journalists were warning that the initial evidence from South Africa — suggesting that Omicron was milder than other variants — might turn out to be a mirage. It has turned out to be real.
  5. "Lung tissue study sheds light on fast Omicron spread". CIDRAP. Archived from the original on 16 December 2021. Retrieved 25 December 2021.
  6. Lewnard, Joseph A.; Hong, Vennis X.; Patel, Manish M.; Kahn, Rebecca; Lipsitch, Marc; Tartof, Sara Y. (2022-01-11). "Clinical outcomes among patients infected with Omicron (B.1.1.529) SARS-CoV-2 variant in southern California": 2022.01.11.22269045. doi:10.1101/2022.01.11.22269045. S2CID 245851556. {{cite journal}}: Cite journal requires |journal= (help)
  7. Ahmed SF, Quadeer AA, McKay MR (January 2022). "SARS-CoV-2 T Cell Responses Elicited by COVID-19 Vaccines or Infection Are Expected to Remain Robust against Omicron". Viruses. 14 (1): 79. doi:10.3390/v14010079. PMC 8781795. PMID 35062283.
  8. Al Jurdi A, Gassen RB, Borges TD, Lape IT, Morena L, Efe O, et al. (2022-01-06). "Diminished antibody response against SARS-CoV-2 Omicron variant after third dose of mRNA vaccine in kidney transplant recipients": 2022.01.03.22268649. doi:10.1101/2022.01.03.22268649. S2CID 245739956. {{cite journal}}: Cite journal requires |journal= (help)
  9. "How Effective Are COVID-19 Vaccines Against Omicron?". Healthline. 2022-01-07. Retrieved 2022-01-17.