Risk factors and risk groups

This section is aimed at assisting public health professionals and is based on an ongoing rapid review of the latest evidence.

(Latest update 21 January 2022)

ECDC’s weekly COVID-19 country overview presents age-specific COVID-19 case notification rates, death rates, and vaccination uptake by country, based on data for confirmed COVID-19 cases reported by EU/EEA countries to The European Surveillance System (TESSy). ECDC’s weekly COVID-19 surveillance report uses data from countries that have reported relevant case-level information throughout the pandemic to estimate age- and sex specific risks, and changes over time in those risks, of hospitalisation, intensive care admission, and death.

Several underlying conditions have a significant independent effect on severe COVID-19 outcomes. Severity of COVID-19 is associated with increased age, pre-existing medical conditions and the male sex [1-3]. Underlying health conditions reported among adult patients with severe COVID-19 disease include diabetes [4-6], obesity [4,7], hypertension [3,4], history of heart failure [4,8], ischaemic heart disease [4,9,10] solid organ tumours [4,11], chronic obstructive pulmonary disease (COPD) [4,12], chronic respiratory disease [4], chronic kidney disease [4,11,13], immune compromised status [4], cancer [4,14,15], neurological conditions [4,16], smoking [4,17], and pregnancy [9,15]. Severe disease is here defined as admission to a hospital/intensive care unit (ICU), mechanical ventilation, or death.

With regards to mortality among hospitalised COVID-19 cases, high-certainty evidence in age- and sex-adjusted analyses identified diabetes mellitus, renal disease and dementia as significant risk factors for mortality. Furthermore, there is moderate certainty evidence that ischaemic heart disease, stroke, solid organ tumours and obesity are also risk factors. Mortality among cases detected in the community setting is associated with a history of heart failure, stroke, diabetes, and end-stage renal disease. There is moderate to high certainty evidence of an association between hospitalisation for COVID-19 and diabetes, heart failure, COPD, renal disease, obesity, and ischaemic heart disease in the community setting [4].

Age is a very important predictor of severe COVID-19. The risk of severe outcomes increases sharply with increasing age, even after controlling for other potential confounding factors, including sex and underlying conditions. Age is also an important effect modifier in the associations between certain underlying conditions and severe COVID-19 outcomes. While some pre-existing medical conditions are known risk factors for severe disease and ICU admission in all age groups, including children and adolescents [10,18-21], it is still not fully understood how these pre-existing conditions influence the course of COVID-19. The absolute probability of being hospitalised or dying increases with age, but findings indicate that a younger person with certain underlying conditions may have the same or even a higher probability of severe outcome than an older person without these conditions. Based on the analysis of 820 404 symptomatic paediatric cases reported by 10 EU Member States between August 2020 and October 2021, there is an increased risk of severe outcomes in cases with comorbidities such as cancer, diabetes, cardiac or lung disease. However, most (83.7%) hospitalised children had no reported comorbidity [21]. This is relevant for age and risk-factor based prioritisation of vaccination, particularly among young people [22].

Residents of long-term care facilities and nursing homes

(Latest update 21 January 2022)

Residents of long-term care facilities (LTCFs) are a medically and socially vulnerable group [23]. Their medical vulnerability to COVID-19 is associated with increased age and the prevalence of underlying health conditions [24,25]. Their social vulnerability can be exacerbated by non-pharmaceutical interventions against COVID-19 that limit physical personal interactions or affect access to health services, with consequences including feelings of abandonment and loneliness [25-27].

LTCFs are relatively closed and high-occupancy settings. In the EU/EEA, the vast majority are nursing homes, residential homes and ‘mixed facilities’ [28,33] . All EU/EEA countries have experienced rapid increases in the incidence of outbreaks and fatal cases of COVID-19 in LTCFs [23,29,30].

Outbreaks of COVID-19 among LTCF residents have commonly spread rapidly, with high attack rates and high case fatality rates [31]. This has been fuelled by the transmission dynamics of COVID-19, including the potential for asymptomatic transmission among and between staff and residents [31-34]. Factors that have hampered the response to COVID-19 in LTCFs have included insufficient availability of personal protective equipment (PPE) and of human resources; insufficient training in IPC, including use of PPE and case management, and reduced access to essential healthcare services [23,27,33,35-39]. Furthermore, there are substantial differences in the organisation of long-term care between and within European countries, affecting infectious disease preparedness and response in LTCFs. These differences were documented by the European Social Policy Network (ESPN), in its 2018 report for the European Commission Directorate-General for Employment, Social Affairs and Inclusion [37], and in related country reports [38].

The body of evidence regarding the effectiveness and population-level impact of COVID-19 vaccines has been increasing [40]. There is evidence that vaccination significantly reduces viral load as well as symptomatic and asymptomatic infections in vaccinated individuals, which could translate into reduced transmission, although the vaccine efficacy varies by vaccine product, target group and variant of concern [40,41]. In COVID-19 outbreaks in LTCFs with the Delta variant that occurred in the EU/EEA between 5 July and 3 October 2021 (i.e., mostly before administration of additional vaccine doses), the protective effect of vaccines was shown to be maintained in outbreaks with low attack rates (AR<20%), but not in outbreaks with higher attack rates (AR≥20%). This suggests a relationship between higher exposure to the virus and breakthrough infections and emphasises the importance of early outbreak detection and rapid containment through effective infection prevention and control (IPC) measures [42].

Further information on ECDC’s options for intervention to prevent transmission and implement testing strategies for COVID-19 in LTCFs can be found in the following documents:

• ‘Infection prevention and control and preparedness for COVID-19 in healthcare settings’ [27]
• ‘Surveillance of COVID-19 in long-term care facilities in the EU/EEA [23]
• ‘COVID-19 testing strategies and objectives’ [43]
• ‘Guidelines for the implementation of non-pharmaceutical interventions against COVID-19’ [26]
• ‘Guidance for discharge and ending isolation of people with COVID-19’ [41].

For more information and resources, see Prevention and control of COVID-19 in long-term care facilities [29].

Additionally, there are several LTCF types that may benefit from specific provisions for COVID-19, because LTCFs include diverse institution types. In Europe, these might also include hospital long-term care wards, hostels (without any type of nursing care), sheltered care homes, day centres, home-based centres and facilities for protected living [23]. If special provisions are not available for these settings, guidance documents that apply to LTCFs and to community care may prove useful. ECDC’s ‘Guidance on the provision of support for medically and socially vulnerable populations in EU/EEA countries and the United Kingdom during the COVID-19 pandemic’ [24] contains considerations for institutions supporting the homeless and people with alcohol or drug dependence.