SARS-CoV-2 variants of concern and variants under investigation in England: Technical briefing 32
Household transmission risk remains higher for Omicron than for Delta (adjusted OR 2.9; 95% CI 2.4-3.5, p <0.001), as does secondary attack rate (e.g. 15.8% for household contacts of confirmed Omicron cases compared to 10.3% for Delta).
Source:
UK Health Security Agency
Resource links:
Risk assessment for SARS-CoV-2 variant: Omicron VOC-21NOV-01 (B.1.1.529)
SPS commentary:
The latest Omicron risk assessment notes there is a reduction in immune protection against infection with Omicron (including natural and vaccine derived immunity); this assessment is now based on neutralisation data from multiple laboratories, assessment of real world vaccine effectiveness in the UK and an observed increase in the risk of reinfection with Omicron. There are insufficient data to make any assessment of protection against severe disease.
There are insufficient data to fully assess severity. However, on the data available in the UK, there is no signal that supports a difference in the intrinsic virulence of the Omicron virus compared to Delta.