The goal of this observational study is to learn about the clinical characteristics and construction of a predictive model in elderly COVID-19 patients. The main question it aims to answer is the main clinical characteristics and risk factors of elderly COVID-19 patients. Participants will not be asked to do any other intervening measure.

Inclusion Criteria:

• Age greater than or equal to 65 years old;
• COVID-19 was diagnosed with SARS-CoV-2 reverse transcription-polymerase chain reaction positive or rapid antigen test positive or a clinical diagnosis made by the radiological responsible clinician based on signs, symptoms, or radiology consistent with COVID-19;
• Hospitalization more than one day, including patients in emergency.

Exclusion Criteria:

• Age less than 65 years old;
• Pregnancy;
• Hospitalization less than one day;
• Outpatients;
• Patients with missing or incomplete information.

Elderly COVID-19 patients admitted into Xiangya Hospital of Central South University (in Changsha, Hunan) and Xiangya Hospital of Central South University, Jiangxi (in Nanchang, Jiangxi)