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Omicron Variant


Jan 24, 2022

Like all viruses, COVID-19 evolves as it spreads between people over time. These changes may affect different properties of the viruses, such as how easily it spreads, the associated disease severity, or the performance of vaccines, therapeutic medicines, diagnostic tools, or other public health and social measures.

The World Health Organization (WHO), in collaboration with partners, expert networks, national authorities, institutions, and researchers have been monitoring and assessing the evolution of the virus since January 2020. In order to prioritise global monitoring and research to ultimately inform the public of the ongoing response to the COVID-19 pandemic, variants are classified as Variants of Interest (VOIs) and Variants of Concern (VOCs). Classification is based on how easily the variant spreads, how severe the symptoms are, how the variant responds to treatments, and how well vaccines protect against the variant.

The Omicron variant, variant B.1.1.529, was first reported to WHO on 24 November 2021 and was classified as a variant of concern by WHO on 26 November 2021. The Omicron variant has been detected around the world and it is transmitting efficiently. The virus is able to adhere to human cells more easily than other variants and people can be reinfected, even if they have had a previous infection or if they have already been vaccinated. The replication of Omicron happens in the upper respiratory tract, unlike Delta and other variants, including the ancestral strain, which are replicated in the lower respiratory tract in the lungs. This combination of factors allows the virus to spread more easily. Even though studies have shown that the risk of becoming severely ill from Omicron is less than it is for the Delta variant, there is still a large number of people who need clinical care and hospitalization due to the sheer volume of cases.
Vaccinations are still protective against severe illness and death no matter the variant. Everyone has a responsibility to keep themselves safe by adhering to preventive measures: get vaccinated, keep a safe distance from others, wear a mask, avoid crowds, ventilate indoor spaces, and clean your hands frequently.

1. World Health Organization (WHO), Tracking SARS-CoV-2 variants (
2. World Health Organization (WHO), Update on Omicron (
3. World Health Organization (WHO), Statement by Dr Hans Henri P. Kluge, WHO Regional Director for Europe (,-prevent,-prepare)
4. World Health Organization (WHO), Dr Van Kerkhove explains why Omicron is transmitting so efficiently & how to contain the spread (

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