Epidemiological update: Omicron variant of concern (VOC) – data as of 10 December 2021 (12:00)

Confirmed cases have been reported by 21 countries: Austria (17), Belgium (30), Croatia (3), Czechia (5), Denmark (154), Estonia (15), Finland (9), France (59), Germany (28), Greece (3), Iceland (20), Ireland (6), Italy (13), Latvia (5), Liechtenstein (1), the Netherlands (36), Norway (109), Portugal (37), Romania (2), Spain (14) and Sweden (16), according to information from public sources. No new EU/EEA countries have reported the Omicron variant since yesterday. A number of probable cases have also been reported in several countries.



Although the cases that were reported initially were linked to travel, an increasing number of cases are now reported to be acquired within the EU/EEA, including as parts of clusters and outbreaks, with cases also being detected in representative surveillance systems. A preliminary analysis of the data reported to The European Surveillance System (TESSy) shows that imported or travel-related cases account for 22 (13%) cases, while 121 (70%) of the reported cases have been acquired locally, including 78 (45%) cases sampled as part of local outbreak investigations.



EU/EEA countries reporting cases without an epidemiological link to travel outside the EU/EEA include Belgium, Denmark, Finland, Spain, and Iceland. This indicates that undetected community transmission could be ongoing in the EU/EEA.



All cases for which there is available information on severity were either asymptomatic or mild. So far, there have been no Omicron-related deaths reported. This data should be assessed with caution, as the number of confirmed cases is too low to understand if the disease clinical spectrum of Omicron differs from that of previously detected variants.



Countries and territories outside of the EU/EEA have reported 1 800 confirmed cases. The 41 countries reporting confirmed cases are: Argentina, Australia, Bermuda (UK), Botswana, Brazil, Canada, Chile, Cuba, Hong Kong Special Administrative Region, Fiji, Ghana, India, Israel, Japan, Jordan, Kuwait, Lebanon, Malawi, Malaysia, Maldives, Mexico, Namibia, Nepal, Nigeria, Russia, Saudi Arabia, Senegal, Sierra Leone, Singapore, South Africa, South Korea, Sri Lanka, Switzerland, Thailand, Tunisia, Uganda, United Arab Emirates, United Kingdom, United States of America, Zambia and Zimbabwe.

Overall, there were 2 382 confirmed cases reported globally by 62 countries.

Table 1. Confirmed cases of SARS-CoV-2 Omicron VOC reported by public sources, as of 10 December 2021 (12:00)

* Denmark reported 154 cases as confirmed through whole genome sequencing and 642 as confirmed nationally through a variant-specific PCR.

Case definitions

Probable case of SARS-CoV-2 Omicron VOC infection

A person with a positive nucleic acid amplification test (NAAT) or rapid antigen detection test (RADT) for SARS-CoV-2 AND one of the following: S-gene target failure or another PCR-based single nucleotide polymorphism (SNP) assay indicative of the SARS-CoV-2 Omicron VOC or is a contact of a probable or confirmed case of SARS-CoV-2 Omicron VOC infection.

Confirmed case of SARS-CoV-2 Omicron VOC infection

A person with confirmed sequencing result for the SARS-CoV-2 Omicron VOC.

Vaccines and previous infection

Preliminary, not peer-reviewed results[1],[2],[3] from in vitro studies on the neutralising capacity of antibodies from convalescent or post-vaccination sera against the Omicron variant virus have been published. Although different methodologies and types of selected sera have been used, these results consistently show a reduced neutralisation capacity of sera from vaccine recipients and convalescent sera against the Omicron virus as compared to other SARS-CoV-2 variants. However, there is also indication that virus neutralisation by sera from individuals who have been infected prior to being fully vaccinated remains effective against this variant. In vitro neutralisation data do not imply a reduction of vaccine effectiveness, particularly against severe disease outcomes, which will also be influenced by cell-mediated immune responses. However, they provide an indication that there could be reduced vaccine effectiveness, particularly toward preventing infection. Furthermore, these preliminary data need to be confirmed by larger studies including sera from individuals with different immunologic profiles (e.g. having received different vaccine brands or additional vaccine doses, and having experienced different severity of infection), as well as sera collected at different times since infection and/or vaccination.

In order to draw accurate conclusions on the protective effect of the current vaccines against the Omicron variant, robust vaccine effectiveness studies are required.

[1] Cele, S et el. SARS-CoV-2 Omicron has extensive but incomplete escape of Pfizer BNT162b2 elicited neutralization and requires ACE2 for infection. medRxiv [Preprint]. DOI: 10.1101/2021.12.08.21267417. Available at: https://www.medrxiv.org/content/10.1101/2021.12.08.21267417v1

[2] Sheward, D et al. Preliminary Report - Early release, subject to modification Quantification of the neutralization resistance of the Omicron Variant of Concern. [Preprint]. Available at: https://drive.google.com/file/d/1CuxmNYj5cpIuxWXhjjVmuDqntxXwlfXQ/view

[3] Wilhelm, A et al. Reduced Neutralization of SARS-CoV-2 Omicron Variant by Vaccine Sera and monoclonal Antibodies. [Preprint]. DOI: 10.1101/2021.12.07.21267432. Available at: https://doi.org/10.1101/2021.12.07.21267432