Differences in clinical features and mortality in very old unvaccinated patients (≥ 80 years) hospitalized with COVID-19 during the first and successive waves from the multicenter SEMI-COVID-19 Registry (Spain). BMC Geriatr. 2022 Jun 30;22(1):546. doi: 10.1186/s12877-022-03191-4. PMID: 35773622.F.I.:3.08