Latest risk assessment: further spread and potential impact of the SARS-CoV-2 Omicron variant of concern in the EU/EEA, 27 January 2022

Risk assessment

Summary

The SARS-CoV-2 Omicron variant of concern (VOC) is rapidly replacing SARS-CoV-2 Delta in most European Union/European Economic Area (EU/EEA) countries, and is broadly following a west-to-east progression. As pointed out by earlier in vitro and in vivo studies, Omicron can to a degree evade the protective effects of antibodies elicited by vaccination or natural infection according to factors such as number of vaccinations or time since last vaccination, thus leaving large portions of the EU/EEA population susceptible to infection. This has resulted in sharp increases in the number of COVID-19 cases, reaching an unprecedented intensity of community transmission across the region.

In comparison with earlier circulating variants, Omicron infections appear less likely to lead to a severe clinical outcome that requires hospitalisation or ICU admission. Hence, although the current overall 14-day notification rate in the EU/EEA is 2 621 cases per 100 000 population, which is three times higher than the highest peak observed during the pandemic to date, hospitalisation rates and mortality are below the levels observed in earlier pandemic waves. However, the number of cases among older people has been increasing more recently in several EU/EEA countries, and this could result in a delayed increase of severe cases and deaths. Although the reduction in severity is partially due to inherent characteristics of the virus, results from vaccine effectiveness studies have shown that a significant role in preventing severe clinical outcomes from Omicron infection is played by vaccination, with effectiveness against severe illness increasing significantly among people having received three vaccine doses. Since vaccination uptake is variable across EU/EEA countries (country range: 28.4–82.9%, average 69.4%) and since the uptake of booster doses is still at suboptimal levels in the majority of EU/EEA countries (80% of EU/EEA countries with booster uptake among adults below 60% as of week 2-2022), the expected impact of Omicron will vary, but countries with lower vaccine uptake are expected to experience the highest disease burden. Furthermore, given the very high levels of community transmission observed regardless of overall vaccine uptake, leading to many people being sick at the same time, countries with very high vaccine uptake will also likely undergo a period of substantial pressure on their healthcare systems and on the functioning of the society as a whole (mainly through absence from work and education).

Mathematical modelling results demonstrate that there is a substantial proportion of the population that remains vulnerable to severe outcomes across all EU/EEA countries, especially in those with lower vaccination coverage. Static projections show hospitalisations and mortality are expected to have a proportionally greater impact among people 60 years and older but will also impact people younger than 60 years. In response to the high incidence of Omicron, protection against the risk of high hospitalisation burden can be accomplished by increasing overall vaccination uptake, including rapidly administering booster doses, especially in the older and at-risk population, will protect against the risk of high hospitalisation burden. Furthermore, the vaccines and boosters provide additional longer-term benefits for individuals and society (e.g. preventing absence from work or education and post-acute COVID-19 syndrome).

There are no data so far on the incidence of prolonged symptoms after COVID-19 due to Omicron, nor on whether this differs from the incidence of post-COVID syndrome brought about by previously circulating variants of SARS-CoV-2. It is plausible that the large number of cases of Omicron infection may be followed by a high incidence of post-COVID-19 condition, with a proportionally higher incidence among people who are unvaccinated.

While we expect to be moving towards a more sustainable situation with COVID-19 circulating at manageable levels, we currently remain in a public health emergency pandemic situation, and it is important to note that even in a post-pandemic phase SARS-CoV-2 could still periodically cause high levels of strain on healthcare systems and lead to large outbreaks. Thus, moving forward, multi-layered surveillance, preparedness, and response strategies for addressing COVID-19 will be essential. 

Risk assessed

The risk to public health posed by the ongoing spread of Omicron in the EU/EEA is assessed in this update.

Omicron is currently the dominant variant in several EU/EEA countries. In some of these countries, the peak of incidence appears to have been reached recently. Omicron is expected to become dominant in all other EU/EEA countries in the coming weeks. The combination of higher growth rate and immune evasion have contributed to the steady increase in the proportion of cases caused by Omicron, and the replacement of the previously dominant Delta variant. Due to the very high circulation of Omicron in most EU/EEA countries, the probability of infection for the EU/EEA population in the coming weeks is considered to be VERY HIGH.

Depending on the situation in countries, the exponential rise in cases is expected to have a HIGH to VERY HIGH impact of in terms of disease burden, pressure on society and strain on healthcare systems through increased hospitalisations and staff absences across different sectors, including among healthcare workers in the immediate coming weeks.

  • In counties where COVID-19 vaccination coverage for the complete primary series is higher than 75% in the total population and there is substantial uptake of booster doses among at-risk individuals, ECDC modelling results indicate that while sustained circulation of Omicron continues the high incidence of cases in the community can still result in severe infections among the residual unvaccinated or partially vaccinated population, and there is a residual risk of severe infection among fully vaccinated people belonging to high risk groups, with a HIGH impact on healthcare and society. For these countries the impact is expected to be HIGH.
  • Countries where COVID-19 vaccination coverage for the complete primary series is lower than 75% in the total population and where the uptake of booster doses among at-risk individuals is suboptimal will experience a higher impact. For these countries the impact is expected to be VERY HIGH.

Of particular concern are countries where vaccine uptake among risk groups has remained low and where Omicron infection has not yet reached its peak. Based on the factors outlined above and considering the different epidemiological situations in EU/EEA countries, the overall public health and societal risk posed by the ongoing spread of Omicron in the EU/EEA is assessed as HIGH to VERY HIGH.

Options for response

Vaccination remains a key component of the multi-layered approach needed to reduce the impact of Omicron, while also addressing the ongoing circulation of Delta. All efforts should be made to increase uptake of the primary vaccination course in people who are currently unvaccinated or partially vaccinated. Furthermore, all eligible adults should be offered a booster dose starting from three months after completing the primary vaccination series. A timely administration of booster doses according to national recommendations is expected to have a significant effect in reducing the impact of Omicron infections.

Given the current epidemiological situation within the EU/EEA, the maintenance of key non-pharmaceutical interventions (NPIs) is crucial over the immediate future in order to ensure that the intensity of Omicron circulation remains at manageable levels. These NPIs include physical distancing, consistent and correct mask wearing, avoiding crowded situations, teleworking when possible, staying home when ill, and maintenance of hand and respiratory hygiene, together with good ventilation of indoors settings. The use of face masks should be considered also in crowded outdoor settings. The key to NPI effectiveness is good compliance and prompt implementation in response to the worsening of epidemiological indicators of community transmission. Given the risk of Omicron infection among vaccinated people, measures should be implemented at population level with no exemptions based on vaccination status. Of particular importance is the prevention and control of infections in healthcare settings, where staff shortages due to Omicron infections are being observed and where outbreaks among people with underlying health conditions will be of significant impact.

Countries where vaccine uptake among risk groups has remained very low and where Omicron infection has not yet reached its peak should consider a rapid, proactive implementation of NPIs and business continuity plans to reduce the impact of Omicron.

Genomic surveillance of currently circulating variants remains of high importance and Whole Genome Sequencing (WGS), or at least complete or partial S-gene sequencing, should be performed, according to the epidemiological and testing capacity situation. This is to ensure the timely identification of any emerging new variants.

When testing capacity is severely limited, priority should be given to hospitalised patients, older people, healthcare workers, and other high-risk groups. If comprehensive testing of all those presenting with symptoms is not feasible, a representative subset of symptomatic cases should be tested, preferably by RTPCR. Multiplex RT-PCR assays with SARS-CoV-2 and other respiratory viruses (e.g. influenza virus and RSV) can be considered for diagnosis of respiratory infections in healthcare settings. In the current high prevalence situation, priority does not need to be given to confirming positive results from a rapid antigen detection test (RADT) by a second method, as the positive predictive value of RADTs is high.

Given the very high attack rate of Omicron infections in the population, and taking into account the fact that 70% of the EU/EEA population has completed its primary vaccination course, it is expected that at the end of the ongoing Omicron wave the vast majority of the EU/EEA population will have built a degree of cellular immunity against SARS-CoV-2. Although the virus will continue to evolve and new variants will emerge, it is likely that until a major virus genomic shift occurs most of the EU/EEA population will have a degree of protection against severe illness. This may result in a prolonged period of ongoing manageable COVID-19 impact in the population, during which Member States should focus on strengthening their surveillance, healthcare systems, and overall pandemic preparedness. Meanwhile, researchers and vaccine manufacturers should prioritise the development of variant-independent vaccines and of vaccines that are more protective against infection and that confer a longer lasting immunity.

Updated assessment on all variants of concern