Please see the attached E-book for:
“Investigation of a SARS-CoV-2 B.1.1.529 (Omicron) Variant Cluster —
Nebraska, November–December 2021”
Link when live: https://www.cdc.gov/mmwr/volumes/70/wr/mm705152e3.htm?s_cid=mm705152e3_w
Enhancing Readiness for Omicron (B.1.1.529): Technical Brief and Priority Actions for Member States
Enhancing Readiness for Omicron (B.1.1.529): Technical Brief and Priority Actions for Member States (who.int)
- 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 variant is a highly divergent variant with a high number of mutations, including 26-32 in the spike protein, some of which are concerning and may be associated with humoral immune escape potential and higher transmissibility.
- As of 16 December 2021, the Omicron variant has been identified in 89 countries across all six WHO regions. Current understanding of the Omicron variant will continue to evolve as more data becomes available.
- The overall threat posed by Omicron largely depends on four key questions, including: (1) how transmissible the variant is; (2) how well vaccines and prior infection protect against infection, transmission, clinical disease and death; (3) how virulent the variant is compared to other variants; and (4) how populations understand these dynamics, perceive risk and follow control measures, including public health and social measures. Public health advice is based on current information and will be tailored as more evidence emerges around those key questions.
- There is consistent evidence that Omicron has a substantial growth advantage over Delta. It is spreading significantly faster than the Delta variant in countries with documented community transmission, with a doubling time between 1.5–3 days. Omicron is spreading rapidly in countries with high levels of population immunity and it remains uncertain to what extent the observed rapid growth rate can be attributed to immune evasion, intrinsic increased transmissibility or a combination of both. However, given current available data, it is likely that Omicron will outpace Delta where community transmission occurs.
- There are still limited data on the clinical severity of Omicron. More data are needed to understand the severity profile and how severity is impacted by vaccination and pre-existing immunity. Hospitalizations in the UK and South Africa continue to rise, and given rapidly increasing case counts, it is possible that many healthcare systems may become quickly overwhelmed.
- Preliminary data suggest that there is a reduction in neutralizing titres against Omicron in those who have received a primary vaccination series or in those who have had prior SARS-CoV-2 infection , which may suggest a level of humoral immune evasion.
- There are still limited available data, and no peer-reviewed evidence, on vaccine efficacy or effectiveness to date for Omicron. Preliminary findings of vaccine effectiveness studies (test-negative design) were obtained from South Africa and England, the United Kingdom. Available preliminary data to be interpreted with caution as the designs may be subject to selection bias and the results are based on relatively small numbers. Results from England indicate a significant reduction in vaccine effectiveness against symptomatic disease for Omicron compared to Delta after two vaccine doses of either Pfizer BioNTech-Comirnaty or AstraZeneca-Vaxzevria vaccines. There was, however, higher effectiveness two weeks after a Pfizer BioNTech-Comirnaty booster, which was slightly lower or comparable to that against Delta. A non peer-reviewed study by South Africa researchers using private health insurance data reported reductions in vaccine effectiveness of the Pfizer BioNTech-Comirnaty vaccine against infection, and to a lesser degree against hospitalization. Details about the methods or results were not available at the time of writing.
- The diagnostic accuracy of routinely used PCR and antigen-based rapid diagnostic test (Ag-RDT) assays does not appear to be impacted by Omicron. Most Omicron variant sequences reported include a deletion in the S gene, which can cause an S gene target failure (SGTF) in some PCR assays. Though a minority of publicly-shared sequences lack this deletion, SGTF can be used as a proxy marker to screen for Omicron. However, confirmation should be obtained by sequencing, as this deletion can also be found in other VOCs (e.g. Alpha and subsets of Gamma and Delta) circulating at low frequencies globally.
- Therapeutic interventions for the management of patients with severe or critical COVID-19 associated with the Omicron variant that target host responses (such as corticosteroids, and interleukin 6 receptor blockers) are expected to remain effective. However, preliminary data from preprint publications suggest that some of the monoclonal antibodies developed against SARS-CoV-2 may have decreased neutralization against Omicron. Monoclonal antibodies will need to be tested individually for their antigen binding and virus neutralization, and these studies should be prioritized
To read the full document, click here:
To view previous versions of this technical brief, please see the links below. The current version of all WHO information products and publications is authoritative.
CDC is working with the Minnesota Department of Health and the New York City Department of Health and Mental Hygiene to investigate a confirmed case of COVID-19 caused by the Omicron variant. The individual, a resident of Minnesota, developed mild symptoms on November 22 and sought COVID-19 testing on November 24. The person has since recovered. The individual traveled to New York City and attended the Anime NYC 2021 convention at the Javits Center from November 19-21, 2021.
CDC recommends people follow COVID-19 prevention strategies. Everyone 5 years and older should get vaccinated and get a booster shot, if recommended. Get tested if you have symptoms and stay home if you are sick.
The following is attributable to CDC Director, Dr. Rochelle Walensky
“CDC has been actively monitoring and preparing for this variant. We have been working closely with Minnesota’s Department of Health and will continue to work diligently with other U.S. and global public health and industry partners as we learn more. CDC has expanded its capacity for genomic sequencing over the past nine months and we have more tools to fight the variant than we had at this time last year from vaccines to boosters to the prevention strategies that we know work including masking in indoor public settings, washing your hands frequently and physical distancing. These methods work to prevent the spread of COVID-19, no matter the genetic sequence.”
First confirmed case of Omicron variant detected in the United States
The California and San Francisco Departments of Public Health have confirmed that a recent case of COVID-19 among an individual in California was caused by the Omicron variant (B.1.1.529). The individual was a traveler who returned from South Africa on November 22, 2021. The individual, who was fully vaccinated and had mild symptoms that are improving, is self-quarantining and has been since testing positive. All close contacts have been contacted and have tested negative.
Genomic sequencing was conducted at the University of California, San Francisco and the sequence was confirmed at CDC as being consistent with the Omicron variant. This will be the first confirmed case of COVID-19 caused by the Omicron variant detected in the United States.
On November 26, 2021, the World Health Organization (WHO) classified a new variant, B.1.1.529, as a Variant of Concern and named it Omicron and on November 30, 2021, the United States also classified it as a Variant of Concern. CDC has been actively monitoring and preparing for this variant, and we will continue to work diligently with other U.S. and global public health and industry partners to learn more. Despite the detection of Omicron, Delta remains the predominant strain in the United States.
The recent emergence of the Omicron variant (B.1.1.529) further emphasizes the importance of vaccination, boosters, and general prevention strategies needed to protect against COVID-19. Everyone 5 and older should get vaccinated boosters are recommended for everyone 18 years and older.
For more information on the Omicron variant visit https://www.cdc.gov/coronavirus/2019-ncov/variants/index.html.