Examine suggests SARS-CoV-2 Omicron confirmed elevated family transmission and immune evasion in Norway

In a latest examine posted to the medRxiv* preprint server, a crew of researchers from Norway used contact tracing knowledge to measure and examine the family secondary assault fee (SAR) of the extreme acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron and Delta variants at a time of prominence of each variants within the nation.

Study: Increased household transmission and immune escape of the SARS-CoV-2 Omicron variant compared to the Delta variant: evidence from Norwegian contact tracing and vaccination data. Image Credit: Novikov Aleksey/ShutterstockExamine: Elevated family transmission and immune escape of the SARS-CoV-2 Omicron variant in comparison with the Delta variant: proof from Norwegian contact tracing and vaccination knowledge. Picture Credit score: Novikov Aleksey/Shutterstock

By the tip of 2021, the Omicron variant of concern (VoC) (B.1.1.529 BA.1) had quickly unfold throughout the globe. In Norway, the Omicron variant took over the Delta variant and by the second week of January 2022, it was detected in >90% of weekly screened nationwide samples.

The immune evasion by the Omicron variant is a vital contributor to the excessive transmissibility seen with this variant. As a result of extremely evasive nature of this VoC, there’s a want for related and well timed measures to grasp the transmissibility and danger of an infection on the inhabitants degree by the Omicron variant.

Examine design

On this analysis work, the researchers carried out a cohort examine between December 2021 and January 2022, utilizing knowledge collected from the coronavirus illness 2019 (COVID-19) pandemic preparedness register of the Norwegian authorities, referred to as Beredt C19. This registry collected data relating to SARS-CoV-2-positive Norwegian residents, testing dates, detection of variants, data of vaccinations, and demographic options.

The register acquired contact tracing knowledge digitally from Norwegian municipalities aiding the linking of index circumstances with traced contacts. The examine inhabitants consisted of registered households and the first circumstances have been outlined as the primary individual within the households who have been SARS-CoV-2 constructive both with the Omicron or Delta variant in the course of the examine interval.


The researchers noticed that in households, the general SAR was greater with the SARS-CoV-2 Omicron variant, 41% (CI95: 38-44) as in contrast with the Delta variant 35% (CI95: 31-38). In main circumstances of youngsters youthful than 16 years, there was no vital distinction in SAR between the Omicron and Delta variants. Equally, no vital distinction in SAR was noticed between the Omicron and Delta variants within the households with main circumstances of 40% vs 35% in non-vaccinated, and 47% vs 45% in contacts.

In households with absolutely vaccinated contacts, the danger of an infection was greater with the Omicron variant (RR: 1.37; CI95: 1.15- 1.64) relative to the Delta variant, whereas a major distinction was not noticed in contacts vaccinated with the booster. SAR was decrease in households with circumstances of booster-vaccinated circumstances and contacts, in comparison with households with non-vaccinated circumstances and contacts. Within the family contacts, there was the next danger of SARS-CoV-2 transmission (RR: 5.75; CI95: 1.32-100) with the Omicron variant within the booster-vaccinated main circumstances as in comparison with the Delta variant, with a decrease relative danger (RR: 1.18; CI95: 1.04-1.46) in absolutely vaccinated main circumstances.

In grownup contacts with a booster vaccination, vaccine effectiveness (VE) was decrease for the Omicron variant (47%) as in comparison with the Delta variant (62%), but it surely was greater for absolutely vaccinated circumstances. Within the absolutely vaccinated circumstances, safety in opposition to an infection with the Omicron variant was 16%, whereas with the Delta variant it was 46%.

Whereas measuring the danger of an infection, the researchers noticed no vital variations as stratified by gender, age group, and time because the final dose in absolutely vaccinated circumstances.


The examine findings indicated {that a} excessive SAR in family contacts circumstances contaminated with the SARS-CoV-2 Omicron variant in Norway is because of the decrease effectiveness of the vaccines and never attributable to the excessive transmissibility of the Omicron variant. The outcomes of the examine additional instructed that booster vaccination has a restricted impact in stopping the transmission of the SARS-CoV-2 Omicron variant.

*Essential discover

medRxiv publishes preliminary scientific studies that aren’t peer-reviewed and, due to this fact, shouldn’t be thought to be conclusive, information scientific follow/health-related habits, or handled as established data.

Journal reference:

  • Neda Jalali, Hilde Kjelgaard Brustad, Arnoldo Frigessi, Emily Ann MacDonald, Hinta Meijerink, Siri Laura Feruglio, Karin Maria Nygård, Gunnar Øivind Isaksson Rø, Elisabeth Henie Madslien, Birgitte Freiesleben de Blasio. (2022) Elevated family transmission and immune escape of the SARS-CoV-2 Omicron variant in comparison with the Delta variant: proof from Norwegian contact tracing and vaccination knowledge. medRxiv. doi: https://doi.org/10.1101/2022.02.07.22270437 https://www.medrxiv.org/content material/10.1101/2022.02.07.22270437v2


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