1. Bachmann MF, Mohsen MO, Zha L, Vogel M, Speiser DE. SARS-CoV-2 structural features may explain limited neutralizing-antibody responses. npj Vaccines. Nature Research; 2021;6:1–4.
2. McKeigue PM, Colhoun HM. Evaluation of “stratify and shield” as a policy option for ending the COVID-19 lockdown in the UK. medRxiv. Cold Spring Harbor Laboratory Press; 2020;2020.04.25.20079913.
3. World Health Organization. Fair allocation mechanism for COVID-19 vaccines through the COVAX Facility [Internet]. 2020 [cited 2021 Jan 9]. p. 1–17. Available from: https://www.who.int/publications/m/item/fair-allocation-mechanism-for-covid-19-vaccines-through-the-covax-facility
4. Smith GD, Spiegelhalter D. Shielding from covid-19 should be stratified by risk. BMJ. BMJ Publishing Group; 2020;369.
5. Persad G, Peek ME, Emanuel EJ. Fairly Prioritizing Groups for Access to COVID-19 Vaccines. JAMA - J. Am. Med. Assoc. American Medical Association; 2020;324:1601–2.
6. Huang C, Wang Y, Li X, Ren L, Zhao J, Hu Y, et al. Clinical features of patients infected with 2019 novel coronavirus in Wuhan, China. Lancet. Lancet Publishing Group; 2020;395:497–506.
7. Zhou F, Yu T, Du R, Fan G, Liu Y, Liu Z, et al. Clinical course and risk factors for mortality of adult inpatients with COVID-19 in Wuhan, China: a retrospective cohort study. Lancet. Lancet Publishing Group; 2020;395:1054–62.
8. Petrilli CM, Jones SA, Yang J, Rajagopalan H, O’Donnell L, Chernyak Y, et al. Factors associated with hospital admission and critical illness among 5279 people with coronavirus disease 2019 in New York City: Prospective cohort study. BMJ. BMJ Publishing Group; 2020;369.
9. Wynants L, Van Calster B, Collins GS, Riley RD, Heinze G, Schuit E, et al. Prediction models for diagnosis and prognosis of covid-19: Systematic review and critical appraisal. BMJ. BMJ Publishing Group; 2020;369:26.
10. DeCapprio D, Gartner J, McCall CJ, Burgess T, Kothari S, Sayed S. Building a COVID-19 vulnerability index. medRxiv. medRxiv; 2020;
11. Monterde D, Vela E, Clèries M, Garcia-Eroles L, Roca J, Pérez-Sust P. Multimorbidity as a predictor of health service utilization in primary care: A registry-based study of the Catalan population. BMC Fam. Pract. BioMed Central Ltd.; 2020;21.
12. Ministry of Economic Affairs and Digital Transformation (Spain). Death records due to COVID-19 in Catalonia. Segregated by gender and region - Dataset | datos.gob.es [Internet]. [cited 2021 Mar 9]. Available from: https://datos.gob.es/en/catalogo/a09002970-registro-de-defunciones-por-covid-19-en-catalunya-segregacion-por-sexo-y-comarca
13. Ministry of Economic Affairs and Digital Transformation (Spain). COVID-19 incidence in Catalonia - Dataset | datos.gob.es [Internet]. [cited 2021 Mar 9]. Available from: https://datos.gob.es/en/catalogo/a09002970-incidencia-del-covid-19-en-cataluna
14. Dueñas-Espín I, Vela E, Pauws S, Bescos C, Cano I, Cleries M, et al. Proposals for enhanced health risk assessment and stratification in an integrated care scenario. BMJ Open. 2016;6:e010301.
15. Monterde D, Vela E, Clèries M, Grupo colaborativo GMA. [Adjusted morbidity groups: A new multiple morbidity measurement of use in Primary Care]. Atención Primaria. 2016;48:674–82.
16. Bergman J, Ballin M, Nordström A, Nordström P. Risk factors for COVID-19 diagnosis, hospitalization, and subsequent all-cause mortality in Sweden: a nationwide study. Eur. J. Epidemiol. Springer Science and Business Media B.V.; 2021;36.
17. Elliott J, Bodinier B, Whitaker M, Delpierre C, Vermeulen R, Tzoulaki I, et al. COVID-19 mortality in the UK Biobank cohort: revisiting and evaluating risk factors. Eur. J. Epidemiol. Springer Science and Business Media B.V.; 2021;36.
18. Gulbech Ording A, Toft Sørensen H. Concepts of comorbidities, multiple morbidities, complications, and their clinical epidemiologic analogs. Clin. Epidemiol. Dove Press; 2013;5:199–203.
19. Huntley AL, Johnson R, Purdy S, Valderas JM, Salisbury C. Measures of multimorbidity and morbidity burden for use in primary care and community settings: A systematic review and guide. Ann. Fam. Med. Annals of Family Medicine, Inc; 2012;10:134–41.
20. Monterde D, Vela E, Clèries M, García Eroles L, Pérez Sust P. Validity of adjusted morbidity groups with respect to clinical risk groups in the field of primary care. Aten. Primaria. Elsevier Doyma; 2019;51:153–61.
21. Monterde D, Vela E, Clèries M, Garcia-Eroles L, Roca J, Pérez-Sust P. Multimorbidity as a predictor of health service utilization in primary care: A registry-based study of the Catalan population. BMC Fam. Pract. BioMed Central Ltd.; 2020;21:39.
22. Del Valle DM, Kim-Schulze S, Huang HH, Beckmann ND, Nirenberg S, Wang B, et al. An inflammatory cytokine signature predicts COVID-19 severity and survival. Nat. Med. Nature Research; 2020;1–8.
23. Ellinghaus D, Degenhardt F, Bujanda L, Buti M, Albillos A, Invernizzi P, et al. Genomewide Association Study of Severe Covid-19 with Respiratory Failure. N. Engl. J. Med. NLM (Medline); 2020;383:1522–34.