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Background This study applies an umbrella review approach to summarise the global evidence on the risk of severe COVID-19 outcomes in patients with pre-existing health conditions. Methods Systematic reviews (SRs) were identified in PubMed, Embase/Medline and seven pre-print servers until December 11, 2020. Due to the absence of age-adjusted risk effects stratified by geographical regions, a re-analysis of the evidence was conducted. Primary studies were extracted from SRs and evaluated for inclusion in the re-analysis. Studies were included if they reported risk estimates (odds ratio (OR), hazard ratio (HR), relative risk (RR)) for hospitalisation, intensive care unit admission, intubation or death. Estimated associations were extracted from the primary studies for reported pre-existing conditions. Meta-analyses were performed stratified for each outcome by regions of the World Health Organization. The evidence certainty was assessed using GRADE. Registration number CRD42020215846. Results In total, 160 primary studies from 120 SRs contributed 464 estimates for 42 pre-existing conditions. Most studies were conducted in North America, European, and Western Pacific regions. Evidence from Africa, South/Latin America, and the Eastern Mediterranean region was scarce. No evidence was available from the South-East Asia region. Diabetes (HR range 1.2–2.0 (CI range 1.1–2.8)), obesity (OR range 1.5–1.75 (CI range 1.1–2.3)), heart failure (HR range 1.3–3.3 (CI range 0.9–8.2)), COPD (HR range 1.12–2.2 (CI range 1.1–3.2)) and dementia (HR range 1.4–7.7 (CI range 1.2–39.6)) were associated with fatal COVID-19 in different regions, although the estimates varied. Evidence from Europe and North America showed that liver cirrhosis (OR range 3.2–5.9 (CI range 0.9–27.7)) and active cancer (OR range 1.6–4.7 (CI range 0.5–14.9)) were also associated with increased risk of death. Association between HIV and undesirable COVID-19 outcomes showed regional heterogeneity, with an increased risk of death in Africa (HR 1.7 (CI 1.3–2.2)). GRADE certainty was moderate to high for most associations. Conclusion Risk of undesirable COVID-19 health outcomes is consistently increased in certain patient subgroups across geographical regions, showing high variability in others. The results can be used to inform COVID-19 vaccine prioritisation or other intervention strategies.

Background: This umbrella review summarises the global evidence on the risk of severe COVID-19 outcomes in patients with pre-existing health conditions. Methods: Systematic reviews (SRs) were identified in PubMed, Embase/Medline, and seven pre-print servers until December 11, 2020. Risk estimates (odds ratio (OR), hazard ratio (HR), relative risk (RR)) for hospitalisation, intensive care unit admission, intubation, and death were extracted from primary studies. Meta-analyses were performed stratified by regions of the World Health Organisation. The evidence certainty was assessed using GRADE. Registration number CRD42020215846. Findings: 160 primary studies from 120 SRs contributed 464 estimates for 42 pre-existing conditions. Most studies were conducted in North America, European, and Western Pacific regions. Evidence from Africa, South/Latin America, and Eastern Mediterranean region was scarce. No evidence was available from South-East Asia region. Diabetes (HR 1∙2-2∙0 (1∙1-2∙8)), obesity (OR 1∙5-1∙75 (1∙1-2∙3)), heart failure (HR 1∙3-3∙3(0∙9-8∙2)), COPD (HR 1∙12-2∙2 (1∙1-3∙2)), and dementia (HR 1∙4-7.7 (1∙2-39∙6)) were associated with fatal COVID-19 in different regions, although the estimates varied. Evidence from Europe and North America showed that liver cirrhosis (OR 3∙2-5∙9 (0∙9-27∙7)) and active cancer (OR 1∙6-4∙7 (0∙5-14∙9)) were also associated with increased risk of death. Association between HIV and severe COVID-19 showed regional heterogeneity, with an increased risk of death in Africa (HR 1∙7 (1∙3-2∙2)). GRADE certainty was moderate to high for most associations. Interpretation: Risk of severe COVID-19 is consistently increased in certain patient subgroups across geographical regions, showing high variability in others. The results can be used to inform COVID-19 vaccine prioritisation or other intervention strategies. Funding Statement: Project ImVaCov – German Federal Ministry of Health Declaration of Interests: Authors declare no conflicts of interest.

In Germany, tick-borne encephalitis (TBE) infections mainly occur in southern regions. Despite recent increases in incidence, TBE vaccination coverage remains low, necessitating additional preventive strategies against TBE. Our case-control study in Southern Germany from 2018 to 2020 mapped knowledge/application of tick-protective strategies and identified TBE risk factors. We calculated odds ratios (OR), with 95% confidence intervals (CI). We interviewed 581 cases and 975 matched controls. Most participants recalled lifetime tick bites, mainly while walking, gardening, or hiking. However, only 45% of cases noticed ticks during exposure time; another 12% reported unpasteurized milk intake. While tick-protection knowledge was satisfactory, application lagged behind. Risk factors included dog ownership (OR = 2.45, 95% CI: 1.85–3.24), walks ≥ 4×/week (OR = 2.11, 95% CI: 1.42–3.12), gardening ≥ 4×/week (OR = 1.83, 95% CI: 1.11–3.02), and garden proximity < 250 m of forests (OR = 2.54, 95% CI: 1.82–3.56). Applying ≥2 tick-protective strategies (OR = 0.52, 95% CI: 0.40–0.68) and keeping lawns mowed (OR = 0.63, 95% CI: 0.43–0.91) were inversely associated with TBE. In 2020 (likely pandemic-related), cases reported significantly more walks than previously, potentially explaining the record high case numbers. Our findings provide guidance on targets for TBE prevention. Persons with gardens near forests, frequent outdoor activities, or dogs could particularly benefit from targeted information, including on vaccination and preventing tick bites.