COVID-19(13) age(11) SARS-CoV-2(10) Infection(7) Older(7) Patient(7) severity(6) immunosenescence(6) pandemic(5) outcome(5) Result(5) Health(5) disease(4) syndrome(4) Mild(4) elderly(4) COVID-19 pandemic(4) reported(4) vaccination(4) SARS-CoV-2 vaccine(4) mechanism(4) frailty(4) risk(4) diabetes(4) death(3) COVID-19 patient(3) Immunity(3) IL-6(3) Vaccine(3) feature(3)