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Secondary Attack Rates for Omicron and Delta Variants of SARS-CoV-2 in Norwegian Households

Educational Objective
To identify the key insights or developments described in this article

The new SARS-CoV-2 B.1.1.529 Omicron variant has spread rapidly throughout the world,13 including in countries such as Norway with 90% primary vaccination and increasing booster vaccination coverage.4,5 To enable alignment of infection control measures with the risk posed by the new variant and avoid excessive strain on health systems, estimates of the transmissibility of the Omicron variant are needed.3,4 We assessed the secondary attack rate of Omicron and B.1.617.2 Delta variants in households in Norway.

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Article Information

Accepted for Publication: February 25, 2022.

Published Online: March 7, 2022. doi:10.1001/jama.2022.3780

Corresponding Author: Kjetil Telle, PhD, Cluster for Health Services Research, Norwegian Institute of Public Health, Box 222, Skoyen, NO-0213 Oslo, Norway (kjte@fhi.no).

Author Contributions: Dr Telle had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.

Concept and design: Jørgensen, Nygård, Telle.

Acquisition, analysis, or interpretation of data: All authors.

Drafting of the manuscript: Jørgensen, Nygård, Telle.

Critical revision of the manuscript for important intellectual content: All authors.

Statistical analysis: Jørgensen, Kacelnik, Telle.

Administrative, technical, or material support: Telle.

Supervision: Jørgensen.

Conflict of Interest Disclosures: None reported.

References
1.
Callaway  E .  Heavily mutated Omicron variant puts scientists on alert.   Nature. 2021;600(7887):21-21. doi:10.1038/d41586-021-03552-wPubMedGoogle ScholarCrossref
2.
European Centre for Disease Prevention and Control. Assessment of the further emergence of the SARS-CoV-2 Omicron VOC in the context of the ongoing transmission in the EU/EEA, 18th update. December 15, 2021. Accessed February 9, 2021. https://www.ecdc.europa.eu/en/publications-data/covid-19-assessment-further-emergence-omicron-18th-risk-assessment
3.
Barnard  RC , Davies  N , Pearson  CAB ,  et al. Modelling the potential consequences of the Omicron SARS-CoV-2 variant in England. CMMID Repository. December 11, 2021. Updated December 23, 2021. Accessed December 29, 2021. https://cmmid.github.io/topics/covid19/omicron-england.html
4.
Veneti  L , Bøås  H , Bråthen Kristoffersen  A ,  et al.  Reduced risk of hospitalisation among reported COVID-19 cases infected with the SARS-CoV-2 Omicron BA.1 variant compared with the Delta variant, Norway, December 2021 to January 2022.   Euro Surveill. 2022;27(4):2200077. doi:10.2807/1560-7917.ES.2022.27.4.2200077PubMedGoogle ScholarCrossref
5.
Norwegian Institute of Public Health. Situation report COVID-19—week 50. December 22, 2021. Accessed December 29, 2021. https://www.fhi.no/contentassets/8a971e7b0a3c4a06bdbf381ab52e6157/ukerapport-uke-50-13.12---19.12.21.pdf
6.
Norwegian Institute of Public Health. Emergency preparedness register for COVID-19 (Beredt C19). November 24, 2020. Updated August 26, 2021. Accessed December 29, 2021. https://www.fhi.no/en/id/infectious-diseases/coronavirus/emergency-preparedness-register-for-covid-19/
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Credit Designation Statement: The American Medical Association designates this Journal-based CME activity activity for a maximum of 1.00  AMA PRA Category 1 Credit(s)™. Physicians should claim only the credit commensurate with the extent of their participation in the activity.

Successful completion of this CME activity, which includes participation in the evaluation component, enables the participant to earn up to:

  • 1.00 Medical Knowledge MOC points in the American Board of Internal Medicine's (ABIM) Maintenance of Certification (MOC) program;;
  • 1.00 Self-Assessment points in the American Board of Otolaryngology – Head and Neck Surgery’s (ABOHNS) Continuing Certification program;
  • 1.00 MOC points in the American Board of Pediatrics’ (ABP) Maintenance of Certification (MOC) program;
  • 1.00 Lifelong Learning points in the American Board of Pathology’s (ABPath) Continuing Certification program; and
  • 1.00 credit toward the CME [and Self-Assessment requirements] of the American Board of Surgery’s Continuous Certification program

It is the CME activity provider's responsibility to submit participant completion information to ACCME for the purpose of granting MOC credit.

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