Inclusion Criteria:

1. Confirmed COVID-19, and the nucleic acid test of respiratory specimens such as sputum
or nasopharyngeal swabs is negative twice after the treatment (sampling interval is at
least 24 hours);

2. Negative nucleic acid test of respiratory specimens such as sputum or nasopharyngeal
swabs during screening visits;

3. High-resolution CT of the lung (HRCT) indicates pulmonary fibrosis (thickness of
lobular septum, honeycomb-like changes, with or without bronchial / pleural
distraction);

4. Voluntarily participate in research and sign informed consent.

Exclusion Criteria:

1. Combined with severe heart, lung (diagnosed with interstitial lung disease, bronchial
asthma, chronic obstructive pulmonary disease, etc.), liver and kidney disease or with
endocrine, rheumatic, neurologic, malignant and other systemic diseases;

2. Have been diagnosed with connective tissue disease;

3. Pregnant or lactating women;

4. History of mental disorders, substance abuse or dependence;

5. Have used other anti-pulmonary fibrosis drugs in the past 14 days, such as nidanib,
pirfenidone, penicillamine, colchicine, tumor necrosis factor alpha blocker, imatinib,
glucocorticoid hormones, morphomycodyl esters, azathioprine, cyclophosphamide,
interferon-γ, and traditional Chinese medicine;

6. Researchers consider it inappropriate to participate in research;

7. Participating in other clinical research.