COVID-19(24) participant(11) Older(10) Patient(8) elderly(8) IMPROVE(7) Health(7) Mortality(7) hospital(7) Vaccine(6) Follow-up(6) vaccination(6) age(6) Prevalence(6) objective(6) Comorbidities(5) functional(5) Comorbidity(5) Prevent(5) include(5) SARS-CoV-2(5) with COVID-19(5) affected(5) Appropriate(5) frailty(5) indicated(5) Biomarker(5) Treatment(5) Diagnosis(5) significantly(5)