SARS-CoV-2 Omicron variant
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]

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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]
References
- "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.
- 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.
- 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.
- 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.
- "Lung tissue study sheds light on fast Omicron spread". CIDRAP. Archived from the original on 16 December 2021. Retrieved 25 December 2021.
- 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.
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(help) - 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.
- 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.
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(help) - "How Effective Are COVID-19 Vaccines Against Omicron?". Healthline. 2022-01-07. Retrieved 2022-01-17.