Enhancing Readiness for Omicron (B.1.1.529): Technical Brief and Priority Actions for Member States

On 26 November 2021, WHO designated the variant B.1.1.529 a variant of concern (VOC), on the basis of advice from WHO’s Technical Advisory Group on Virus Evolution. The variant has been given the name Omicron. • Omicron is a highly divergent variant with a high number of mutations, including 26-32 in the spike, some of which are concerning and may be associated with immune escape potential and higher transmissibility. However, there are still considerable uncertainties. • The main uncertainties are (1) how transmissible the variant is and whether any increases are related to immune escape, intrinsic increased transmissibility, or both; (2) how well vaccines protect against infection, transmission, clinical disease of different degrees of severity and death; and (3) does the variant present with a different severity profile. Public health advice is based on current information and will be tailored as more evidence emergences around those key questions. Risk Assessment • Given mutations that may confer immune escape potential and possibly transmissibility advantage, the likelihood of potential further spread of Omicron at the global level is high. Depending on these characteristics, there could be future surges of COVID-19, which could have severe consequences, depending on a number of factors including where surges may take place. The overall global risk related to the new VOC Omicron is assessed as very high. Priority actions for Member States: • Enhance surveillance and sequencing efforts to better understand circulating SARS-CoV-2 variants, including Omicron. Where capacity exists, perform field investigations and laboratory assessments to improve understanding of the characteristics of Omicron. This should include community testing to detect if Omicron is circulating in the community. • As S gene target failure (SGTF) from a widely used PCR test (ThermoFisher TaqPath) is indicated for Omicron, the SGTF can be used as the marker for this variant, which may lead to efficient detection of Omicron. • Report initial cases/clusters associated with Omicron infection to WHO through the IHR mechanism. o Thereafter, report (publicly or through IHR) the proportion of Omicron among sequenced samples (and/or, where available, the proportion of SGTF) • Accelerate COVID-19 vaccination coverage as rapidly as possible, especially among populations designated as high priority who remain unvaccinated or are not yet fully vaccinated. • Use a risk-based approach to adjust international travel measures in a timely manner. See forthcoming WHO advice for international traffic in relation to the SARS-CoV-2 Omicron variant