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29

Omicron SARS-CoV-2 Variant of Concern Identified in King County

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Omicron SARS-CoV-2 Variant of Concern Identified in King County

Health advisory

December 5, 2021

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  • Be aware that a new SARS-CoV-2 variant of concern, Omicron, has been identified in 1 case in each of King, Pierce and Thurston Counties. There is no known connection among these cases.
    • It is likely there are additional unrecognized cases and that local transmission is occurring at low levels currently.
    • The Delta remains the dominant variant causing COVID-19 in the US currently.
  • Information about the human health significance of Omicron is evolving rapidly. Key questions about transmissibility, severity and evasion of immunity from past infection, vaccines, and therapeutics, remain unanswered.
  • CDC has revised international travel guidance.
  • Refer to the recently released CDC Health Advisory and CDC's Omicron webpage for more information.
  • Both PCR and rapid antigen tests are expected to detect the Omicron variant, although gene sequencing is needed to distinguish it from Delta and other SARS-CoV-2 strains.
  • PCR tests that detect S gene target failure are suggestive, but not conclusive evidence of Omicron.
  • At this time, Public Health recommends optimizing COVID-19 prevention measures in healthcare settings and the community to protect against both the currently dominant Delta variant as well as the emergence of a potentially more transmissible Omicron variant.
    • Vaccination, with booster doses for eligible patients, is the single most important prevention measure.
      • Provide and/or facilitate vaccination with both primary series and booster doses for eligible patients. Where possible, actively recall booster-eligible patients for vaccination, especially older adults and other patients with risk factors for severe COVID-19.
    • Assess and improve indoor air quality where necessary through a combination of enhanced ventilation, filtration and/or UV technology (see resources, below).
    • Educate patients regarding the need to mask in indoor public spaces and the benefits of using masks of high quality that fit well.
    • Educate patients about the risk in crowded indoor settings, especially where not all are vaccinated/boosted.
    • Reinforce the need to stay home and isolate away from others if symptoms compatible with COVID-19 develop, and to seek testing if symptomatic or exposed to a suspected or known COVID-19 case, and after travel.
    • Reinforce that layered protections provide the most risk reduction.
    • Immunocompromised patients should consider multiple precautions.
  • Healthcare facilities should use this opportunity to plan for a potential surge in patients with COVID-19 symptoms which may be further exacerbated if simultaneous influenza activity increases locally.
  • Please continue to report all COVID-19 cases immediately to Public Health – Seattle & King County at (206) 296-4774. If there is suspicion that the case has been exposed to the Omicron variant, please mention that in your report

A new SARS-CoV-2 variant, B.1.1.529 lineage, was first detected in Botswana on 11 November 2021 and soon after in South Africa on 14 November 2021. Subsequently cases were found from earlier dates in other countries. This variant was found to have an especially large number of mutations in its genome, raising concerns regarding virus transmissibility and potential for evasion of previously established immunity, either from natural infection or vaccine. This led to the classification by the WHO (on 26 November 2021) of this new variant as a variant of concern (VOC), named Omicron. Soon after, on 30 November 2021, the U.S. SARS-CoV-2 Interagency Group, which includes the CDC, also designated Omicron as a VOC. Since first identified, Omicron has been identified in 40 countries and at least 15 US states.

At present, there are three primary unknowns regarding Omicron: 1) transmissibility, 2) severity, and 3) potential for evasion of immunity, therapeutics, and diagnostic tests. The extensive number of mutations and preliminary data from South Africa suggest Omicron may be significantly more transmissible than Delta.

Also based on limited data, it has been reported (but not confirmed) that severity of illness may be less than with Delta. However, many cases have occurred in younger individuals who are less likely to have severe disease and drawing conclusions from this sample would be premature. Lastly, the potential that this much altered variant will not respond in the same manner to current interventions, especially vaccines, is of significant concern. It is possible that there will be a decrease in neutralizing antibody activity from vaccination which could lead to (less severe) breakthrough infections, although protection against severe disease may very well be preserved. For this reason, booster doses that increase the level and breadth of immune protection are especially important.

However, it is still too soon to make firm conclusions regarding any of the above. We expect more information to be available in the coming weeks. At this time, the combination of tools we've used against Delta, especially vaccination plus boosting, remains the best strategy against both the current Delta outbreak and a potential Omicron outbreak.

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