This brief article is a warning assessed over 15 to 18 December 2021 about the very serious, indeed “major, imminent threat” created by the Omicron variant (Neil Ferguson in Emily Head, Dr Sabine L. van Elsland, “Omicron largely evades immunity from past infection or two vaccine doses“, ICL News, 17 December 2021).
Since the Omicron variant was identified, we have been waiting for further assessments regarding this variant of concern (VoC).
Two such early assessments have been recently published:
- European Centre for Disease Prevention and Control, Assessment of the further emergence and potential impact of the SARS-CoV-2 Omicron variant of concern in the context of ongoing transmission of the Delta variant of concern in the EU/EEA, 18th update – 15 December 2021. ECDC: Stockholm; 2021.
- Neil Ferguson, Azra Ghani, et al., “Report 49 – Growth, population distribution and immune escape of Omicron in England”, Imperial College London, 17 December 2021 – with a Summary by Emily Head, Dr Sabine L. van Elsland, “Omicron largely evades immunity …“, Ibid,).
Other studies are to be expected, however the probability of the situation being imminently very serious is high enough to deliver a warning. Monitoring must of course continue.
Summarised current findings
Imperial College London assessments are for the UK, however, considering past waves, they are excellent indications of what could happen elsewhere in the world.
In a nutshell, Imperial College London findings are as follows:
The very high infectious power of Omicron is confirmed
“The proportion of Omicron among all COVID cases was doubling every 2 days up to December 11th… Reproduction number (R) of Omicron was above 3 over the period studied”.Summary News, Imperial College London 17 Dec 2021.
Younger people seem to be more vulnerable than with previous variants
“The distribution of Omicron by age, region and ethnicity currently differs markedly from Delta, with 18–29-year-olds… having significantly higher rates of infection with Omicron relative to Delta. … the researchers note that given its immune evasion, the age distribution of Omicron infection in the coming weeks may continue to differ from that of Delta.”Abstract Imperial College London 17 Dec 2021
No herd immunity
Earlier natural immunity hardly offers protection.
“Risk of reinfection with the Omicron variant is 5.4 times greater than that of the Delta variant… protection against reinfection by Omicron afforded by past infection may be as low as 19%.”Summary News, Imperial College London 17 Dec 2021.
Vaccination induced immunity strongly or mildly degraded
Vaccination (initial full scheme/two doses) does not offer protection, while the third dose/booster protects less than with the Delta variant.
“Depending on the estimates used for vaccine effectiveness against symptomatic infection from the Delta variant, this translates into vaccine effectiveness estimates against symptomatic Omicron infection of between 0% and 20% after two doses, and between 55% and 80% after a booster dose.”Summary News, Imperial College London 17 Dec 2021.
Note, that as a result of these, the very idea of herd immunity disappears or must be revised, as we warned on 27 January 2021 (see COVID-19 Vaccinations, Hope or Mirage?).
It may be too early to completely assess the severity of the variant, however, so far, severity does not appear to have been lowered compared with Delta:
The study finds no evidence of Omicron having lower severity than Delta,Summary News, Imperial College London 17 Dec 2021.
ECDC warning assessment
Therefore this study reinforces the alerts of the ECDC, very briefly summarised as:
“…We therefore assess the probability of further spread of the Omicron variant in the EU/EEA as VERY HIGH” .
“…We therefore assess the impact of the spread of the Omicron VOC as VERY HIGH.
“…the overall level of risk to public health associated with the further emergence and spread of the SARS-CoV-2 Omicron VOC in the EU/EEA is assessed as VERY HIGH.“ECDC 18th Update
Responses and recommendations
Recommandations are full vaccination plus booster/third dose plus full non pharmaceutical interventions (NPI: “use of face masks, reduced contacts between groups of individuals in social or work settings, teleworking, expanded testing and strong contact tracing”- ECDC, and also disinfection of hands and possibly materials etc.).
“Rapid reintroduction and strengthening of NPIs is necessary”
“Vaccination remains a key component of the multi-layered approach needed to reduce the impact of the Omicron VOC, while also addressing the ongoing circulation of the Delta VOC.”ECDC 18th Update
The ECDC stops shorts of highlighting the possible need for renewed lockdown, and prefers to stress the importance of testing and contact tracing, isolation, increase in health capacities and genomic surveillance.
Some health authorities, such as those of the Netherlands, however, recommend full lockdown: “Dutch health experts advise a full lockdown to slow Omicron -media” Reuters, 18 December 2021.