Study design:

Allocation: Randomized Endpoint classification: Efficacy study Masking: Open label Primary purpose: Treatment Primary endpoint: Incidence of reaching the target serum trough concentration Secondary endpoint: Clinical efficiency, Antibiotic use, acute kidney injury.

This is a prospective randomized control trial. There are two groups, study group and control group. Patients of study group accepted vancomycin strategies decided by a serum trough concentration model, and patients of control group accepted vancomycin dosage decided by attending physician. The primary endpoint is the incidence of reaching the target serum trough concentration, the secondary endpoint are clinical efficiency, antibiotic use and side effects such as acute kidney injury, etc.

Inclusion Criteria:

• Patients with doubted or diagnosed Methicillin-resistant Staphylococcus aureus severe pneumonia, and need vancomycin treatment.
• Sixty years and older.

Exclusion Criteria:

• younger than 60 years old
• Accepted blood purification therapy
• Pregnancy
• Positive HIV antibody titre
• Had known or suspected tuberculosis or other infections caused by fungi at baseline.