Weekly epidemiological update: Omicron variant of concern (VOC) – week 2 (data as of 13 January 2022) EU/EEA
From 20 December 2021 to 2 January 2022, there were 21 EU/EEA countries with adequate sequencing volume that reported an estimated prevalence of Omicron VOC of 46%. COVID-19 case notification and hospital admission rates were high and increasing in most countries, while death and ICU admission rates remained stable. There is still limited evidence suggesting that the observed severity associated with Omicron VOC is lower than that associated with the Delta variant. Early studies suggest that current vaccines may be less effective against Omicron infection, although they still provide protection against hospitalisation and severe disease. Given the exponential growth advantage of Omicron VOC and the high numbers of cases, any potential benefits from a lower observed severity will be short-lived and outpaced by the sheer number of severe outcomes over time.
At the end of week 1 (week ending Sunday, 9 January 2022), the overall epidemiological situation in the EU/EEA was characterised by a high and increasing case notification rate and a high yet stable death rate. An epidemiological situation of high or very high concern was observed in 28 EU/EEA countries. This situation is largely driven by the increasing spread of the Omicron VOC.
The COVID-19 14-day case notification rate for the EU/EEA for week 1 of 2022 was 2 008 per 100 000 population (country range: 227.6 to 5 572). Case notification rates have increased for the past three weeks, and increasing trends were observed in 28 countries. Case notification rates were highest in people aged 15 to 24 years old (3 834 per 100 000), followed by those aged 25 to 49 years old (2 852 per 100 000), and younger than 15 years (1 853 per 100 000). Noticeably, all age groups have registered increasing case notification rates for the previous two weeks.
The 14-day COVID-19 death rate for the EU/EEA for week 1 of 2022 was 49.2 per million population (country range: 10.2 to 142.7). This death rate has been stable for seven weeks. Increasing trends in death rates were observed in nine countries. The death rate peaked in week 2020-W49 at 115 per million population.
The hospital admission rate for the EU/EEA for week 1 of 2022 (data reported by 17 countries) was 15.4 per 100 000 population (country range: 2.4 to 37.3) and has increased for two weeks. Increasing trends of hospital admission rates were observed in eight countries. For six countries, the hospital admission rate was 50% or higher when compared to data during the respective country’s pandemic peak.
The ICU admission rate for the EU/EEA for week 1 of 2022 (data reported by 14 countries) was 1.9 per 100 000 population (country range: 0.5 to 8.4) and has been stable for six weeks. Increasing trends were observed in four countries. In five countries, the ICU admission rate was 50% or higher, when compared to data during the respective country’s pandemic peak.
This weekly epidemiological update provides an overview of the extent to which SARS-CoV-2 Omicron VOC is prevalent in EU/EEA countries, based on the best currently available evidence (as of 13 January 2022). The data are collected from The European Surveillance System (TESSy) or the GISAID EpiCoV database. Please refer to the ECDC Variants of interest and concern in the EU/EEA dashboard or click on the country’s corresponding link for more details. In cases of missing data, EU/EEA countries’ official national or regional websites are used. As a result, the data presentation and completeness might be different depending on the data sources and availability.
As of 13 January 2022, the Omicron variant has been identified in all EU/EEA countries. From 20 December 2021 to 2 January 2022, there were 21 EU/EEA countries with adequate sequencing volume that reported an estimated prevalence of Omicron VOC of 46.4% (range from 1.1% to 98.5%), twice as high as for the previous week.
Countries where Omicron has become the dominant variant (accounting for more than 50% of sequenced viruses) include Austria (89.4%, 2022-01), Belgium (99.7%, 2022-01), Cyprus (70.7%, 2021-52)*, Denmark (95.8%, 2022-01), Finland (99.8%, 2021-52), France (78.6%, 2022-01), Greece (75.5%, 2021-52), Iceland (no national proportion available), Ireland (90.6%, 2021-52)*, Liechtenstein (76.7%, 2022-52)**, Lithuania (>90%, 2022-01), Luxembourg (69.6%, 2021-52), Malta (67%, 2022-01), the Netherlands (87.4%, range between labs 86.8% - 95.7%, 4 January 2022), Norway (85.7%, 2022-01), Portugal (77.2%, 2021-52), Slovenia (67% of cases sequenced on 5 January 2022), Spain (54.8%, 2021-52), and Sweden (61.5%, 2022-01).
Countries where the Omicron variant is present but not dominant include Bulgaria (10.3%, 2022-01), Croatia (no national proportion available), Czechia (24.4%, 2021-52)*, Estonia (12.1%, 2022-01), Germany (40.2%, 2021-52), Hungary (43.1%, 2022-01), Italy (39%, 2022-01), Latvia (16.9%, 2021-52), Poland (20.9%, 2021-52), Romania (42.1%, 2022-01), and Slovakia (13.4%, 2022-01).
Large (20% or higher) increases in the number of cases have been reported in the following countries: Austria, Cyprus, Luxembourg, Finland, Germany, Greece, and Lithuania. For a general overview of the epidemiological COVID-19 situation in the EU/EEA, please see the ECDC weekly Country Overview ReportECDC Country Overview Report.
*Insufficient precision at less than 5% prevalence (more information available here).
** Seven-day average; 79.5% as a daily value. Please note that the data for Liechtenstein are reported together with Swiss data.
Disease severity related to Omicron
Preliminary evidence suggests that infections with the Omicron VOC have a less severe clinical presentation than Delta. However, it is still too early to make a complete assessment of Omicron’s severity.
Not peer-reviewed data from South Africa show that despite the higher number of SARS-CoV-2 cases during the Omicron wave, the hospital admission rates were lower (4.9%) than in the previous waves (Beta 18.9%, Delta 13.7%). Likewise, fewer patients had severe disease (28.8%) than the Beta (60.1%) and Delta (66.8%) waves. However, it is important to consider that 73% of the adult population in the area had already been infected with SARS-CoV-2 before Omicron’s dominance, and that incidental positive patients due to screening were also counted in the Omicron cases. Therefore, no conclusion on the inherent severity of Omicron can be made from these data.
The UKHSA shared a report estimating that Omicron-infected individuals have 50% lower risk to visit or to be admitted to the hospital than people with infection due to Delta (hazard ratio 0.53, 95% CI 0.50-0.57). They also found a 65% lower hospitalisation risk for Omicron cases who had received 2 doses of a vaccine and 81% reduction with 3 doses, compared to unvaccinated.
Another study from Scotland used the national data of individuals with symptomatic Omicron infection and identified a reduced hospitalisation risk compared to Delta cases, while the rate of possible reinfection for Omicron was 10 times that of Delta. Vaccinated individuals with the third vaccine dose had a 57% (95% CI 55-60) lower risk to experience symptoms following Omicron infection.
A recent Canadian report confirmed low hospital admission rates (0.3%) and case fatality (<0.1%) for Omicron cases. Shorter median length of hospital stay and reduced need for respiratory support than the previous variants were also reported in another publication (not peer-review) from Texas.
Similar findings were published in a preprint from Southern California where they also report reduced risk of hospital/ICU admission and mortality for Omicron cases compared to Delta. The median hospital stay duration for symptomatic patients was approximately 70% (~3.4 days) shorter for Omicron infected cases. The added value of this study is the contemporaneous comparison of Omicron and Delta variants co-circulating among the same exposed population.
However, most of studies do not account for waning immunity, neither for the likely large amount of under-ascertained reinfections. This could lead to an overestimation of the decrease in severity.
It usually takes several weeks for the accumulation of clinical outcomes to conclude on the impact of a specific variant in hospital admissions, intensive care need and deaths. It is important to highlight that prior immunity from natural infection and/or vaccination and improved treatment options will contribute to less severe outcomes from subsequent infection. The true risk of severe infection may be underestimated by the large numbers of vaccinated or previously infected people, which was not the case in the beginning of preceding waves. It is also essential to account for the relatively young age of most people who have been infected with Omicron so far, and thus far there are little data on the severity among older age groups and people with underlying risk factors.
Therefore, the clinical profile of Omicron may change with upcoming evidence.
Importantly, the combination of higher growth rate and immune evasion indicate that any potential advantage Omicron may have in terms of decreased severity, could be countered by increased community infection rates leading to substantially additional burden for the hospitals, while primary care may be overburdened even more than during previous waves. As more evidence builds up, a better assessment of clinical outcomes and long-term consequences, such as post-COVID-19 condition will be feasible.
Vaccine effectiveness against infection and/or severe disease due to Omicron
A preprint of a study from Canada assessing the vaccine effectiveness of mRNA vaccines found that two doses of an mRNA vaccine were not protective against Omicron infection (VE 6%, 95% CI: -25-30%). A third dose provided some protection against Omicron infection (VE 37% (95% CI: 19-50%) in the immediate term but substantially less than against Delta (VE 93% (95% CI: 92-94%), ≥7 days after third dose. The study highlights that the results may be confounded by behaviours that were unable to be accounted for and that duration of the protection and effectiveness against severe disease are uncertain.
On 7 January 2022, the United Kingdom’s Health Security Agency (UKHSA) published the results of an updated analysis that estimated the effectiveness of three doses of COVID-19 vaccines against symptomatic disease and hospitalisation in adults aged 65 years or older. In all periods, vaccine effectiveness against symptomatic disease was significantly lower for Omicron compared to Delta and waned to minimal or no effect at 20 weeks after primary vaccination. Nevertheless, protection against hospitalisation was greater than that against symptomatic disease, especially after a booster dose, where estimated vaccine effectiveness against hospitalisation was around 90 to 95% three months after the booster dose and around 50% after 6 months. These results should be interpreted with caution due to the low numbers and the possible biases related to differences in vaccine coverage and exposure to Omicron in different population groups.
Another preprint study from the United States, contracted by the vaccine manufacturer Moderna, reports a vaccine effectiveness of 30.4% (95% CI: 5.0-49.0%) against Omicron infection after two doses of the Spikevax vaccine. A third (booster) dose increased the effectiveness to 62.5% (95% CI: 56.2-67.9%). The study also reports considerably lower vaccine effectiveness against Omicron infection among immunocompromised individuals compared to the general population.
Earlier studies from the UK and Denmark showed significantly reduced and declining vaccine effectiveness against symptomatic disease with Omicron compared to infection with Delta. These studies also reported that a booster dose increased the vaccine effectiveness, although not as efficiently as against infection with Delta. The additional protection from booster doses against infection with Omicron was also confirmed in a recent study from Scotland.
Estimates of vaccine effectiveness against hospitalisation from the UK and South Africa have indicated that the protection against severe disease from Omicron infection is higher (around 70% after primary vaccination) than the protection against mild infections, and that the protection increases after a third dose of vaccine.
The estimates of vaccine effectiveness against the Omicron variant should still be considered as preliminary evidence and may have been subject to possible bias related to differences in vaccine coverage and exposure to Omicron in different population groups. Studies and collection of real-life data are ongoing to further assess the level of protection from the vaccines against transmission, infection, and severe disease.
It is important to consider that vaccine effectiveness should be interpreted in the light of the baseline severity and transmissibility of the Omicron VOC, compared to previous variants.
Effect of severity on population burden of disease
The intrinsic severity of Omicron in a completely susceptible population may be different to the observed severity in a population protected by a combination of vaccine-derived and natural immunity. Generalising the severity observed in different countries is thus becoming increasingly difficult given that the sero-epidemiological situation has been diverging internationally throughout 2021. It is thus important for studies to account for differences in vaccination and (past) infection status and explore possible under-ascertainment, and for countries to collect updated and representative data on the country-level sero-prevalence that separates the vaccination-derived from natural immunity.
It is conceivable that the protection from both vaccines and natural immunity may hold up for a longer time against severe outcomes than the protection against infection, milder disease, and (non-ICU) hospital admissions – similar to what was observed with previous VOCs. However, given the conclusive evidence on the exponential growth advantage of Omicron over Delta with the inconclusive evidence of any proportional change in severity that would only be linear, even a larger reduction in severity will alleviate the pressures felt from increased hospital admissions only for a very short time.
Overall level of risk and options for response:
Based on the current situation and the available evidence, ECDC’s Rapid Risk Assessment 18th Update on the impact of Omicron remains valid: 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.
Over the coming weeks, the very high growth advantage of Omicron is expected to result in even higher overall case notification rates. Such high levels of SARS-CoV-2 transmission may lead to high levels of absence from work including among healthcare and other essential workers and are likely to overwhelm the testing and contact tracing capacities in many EU Member States. The sheer volume of COVID-19 cases anticipated to occur are expected to place considerable strain on healthcare systems and society. ECDC has provided options for adapting quarantine and isolation, particularly when countries face high or extreme pressure on healthcare systems and other functions in society, including essential services.
Please see the ECDC’s Rapid Risk Assessment for epidemiological forecasts and options for response (non-pharmaceutical interventions, health system strengthening, vaccination, testing and contact tracing, and risk communication). ECDC will publish updates on the epidemiological situation, severity, spread, and vaccine effectiveness in short intervals.
Awaiting the availability of further evidence, urgent and strong action is needed to reduce transmission, keep the burden on healthcare systems manageable, and protect the most vulnerable in the coming weeks.
Member States should urgently assess their acceptable levels of residual risks, current healthcare system capacities, and available risk management options (e.g. contingency and business continuity measures, surveillance and testing strategy, quarantine and isolation policy, etc.).
Strengthening of non-pharmaceutical interventions is necessary to reduce ongoing Delta VOC and Omicron VOC transmission and keep the COVID-19-related disease burden manageable. These measures include avoiding large public or private gatherings, extended use of face masks, reduced contacts between groups of individuals in social or work settings, teleworking, and reduced inter-household mixing.
Vaccination remains a key component of the multi-layered approach needed to address the ongoing circulation and reduce the impact of the Delta and Omicron VOCs. Efforts should continue to increase full vaccination uptake in individuals who are currently unvaccinated or partially vaccinated and accelerate the roll-out of booster doses.
Member States are strongly encouraged to conduct and share findings on outbreak investigations and epidemiological studies to inform future risk assessments.