Assessment of the current SARS-CoV-2 epidemiological situation in the EU/EEA, projections for the end-of-year festive season and strategies for response, 17th update

Risk assessment

European Centre for Disease Prevention and Control. Assessment of the current SARS-CoV-2 epidemiological situation in the EU/EEA, projections for the end-of-year festive season and strategies for response, 17th update – 24 November 2021. ECDC: Stockholm; 2021.

This Rapid Risk Assessment assesses the risk posed by the circulation of the Delta variant of SARS-CoV-2 between 1 December 2021 to 31 January 2022, based on modelling scenarios and projected levels of vaccination coverage. Updated forecasts developed for this risk assessment are informed by the latest evidence on SARS-CoV-2 seroprevalence, COVID-19 vaccine effectiveness, and waning vaccine immunity, which are also presented.

Executive summary

Increases in case notifications, hospitalisations and intensive care unit (ICU) admissions for SARS-CoV-2 have been observed in October and early November in the majority of EU/EEA countries, after a period of decline in August and September 2021. This has been driven by circulation of the Delta variant (B.1.617.2) in the context of insufficient vaccine uptake and widespread relaxation of non-pharmaceutical interventions (NPIs). Whilst the burden from COVID-19 is particularly high in a number of countries experiencing low vaccine uptake, there is evidence of rising burden even among countries with higher uptake. The current epidemiological situation is to a large part driven by the high transmissibility of the Delta variant that counteracts the reduction in transmission achieved by the current vaccination rollout in the EU/EEA.

To date, 65.4% of the total population and 76.5% of the adult population in the EU/EEA have been fully vaccinated against COVID-19. The overall pace of weekly increase in vaccine uptake in the EU/EEA is slowing down and is mostly driven by the rollout in younger age groups. Four countries are still reporting less than 50% of full vaccine uptake in the total population. Vaccination continues to successfully avert deaths, reduce hospitalisations and transmission in the EU/EEA, despite the emergence and continued dominance of the Delta variant, which is up to 60% more transmissible than the previously dominant variant, Alpha (B.1.1.7).

Available evidence emerging from Israel and the UK shows a significant increase in protection against infection and severe disease following a booster dose in all age groups in the short term. All EU/EEA countries have begun administration of ‘additional dose’ vaccination (to better protect individuals who mount inadequate immune responses to the primary schedule) and ‘booster’ vaccinations (to improve protection in individuals for whom immunity may wane over time since completing the primary schedule).

The end-of-year festive season is traditionally associated with activities such as social gatherings, shopping and travelling, which pose significant additional risks for intensified transmission of Delta.

Modelling scenarios that consider vaccine uptake (including ‘additional dose’ and ‘booster’ vaccinations), vaccine effectiveness, waning vaccine-induced immunity, vaccination of children, natural immunity and population contact rates, indicate that the potential burden of disease risk in the EU/EEA from the Delta variant is expected to be very high in December and January, unless NPIs are applied now in combination with continued efforts to increase vaccine uptake in the total population.

Modelling forecasts highlight the need for NPIs as an immediate measure to control transmission, in combination with rollout of vaccine booster doses for adults, which should be prioritised for those aged 40 years and over, at least six months after completing a primary vaccine schedule. Booster doses will sustain transmission control beyond the immediate impact of implementing NPIs.