Resveratrol group (treatment group) will be instructed to consume with capsules (1.0 g, orally once a day) for six months.

Placebo group (control group) will be instructed to orally take placebo (edible paraffin, 1.0) once a day.

Resveratrol has been used as a food supplement. Its antiviral properties have been well studied including its inhibitory effect against the coronavirus MERS-CoV. Our previous in vitro and in vivo studies found that the compound had other health benefits such as anti-fibrotic effect.The anti-fibrotic effect will add an extra benefit for resveratrol to fight against COVID-19 as lungs are the most affected organs by the coronavirus, which may result in prolonged fibrotic damage of the lungs even when a patient is recovered from the COVID-19 disease.

Lung function will be assessed by the handheld basic spirometry (forced expiratory volume, FEV and forced vital capacity, FVC). FEV is the parameter to measure how much air the participants can force from their lungs in one second. Lower FEV-1 readings indicate more significant obstruction. FVC is the largest amount of air that the participants can forcefully exhale after breathing in as deeply as they can. A lower than normal FVC reading indicates restricted breathing. The participants will be trained to check these measurements at home and record the data in the patient diary.

All the symptoms will be measured by PRO scores according to the clinical symptoms of COVID-19 rehabilitation patients. The scores will be ranged from 0-4: "0" indicates none; "1" indicates mild; "2" indicates moderate; "3" indicates moderately severe; and '4" indicates severe.

We will also use Borg Category-Ratio 0-10 Scale (Borg CR10 Scale) to measure dyspnea as recommended by the American College of Sports Medicine (ACSM) guidelines for patients with pulmonary diseases (Asha et al., 2012). The Borg Category Ratio 10 (CR10) Scale® (Borg Dyspnea Scale), will be used to rate the patients' dyspnea and overall fatigue level.

Scale:

0=Rest; 0.5=Really Really Easy; 1=Really Easy; 2=Easy; 3=Moderate; 4=Sort of Hard; 5,6=Hard; 7,8,9=Really Hard; 10=Maximal

Lung Function Questionnaire is a simple, brief, self-administered instrument to identify patients appropriate for lung function evaluation by 5 items about the breathing problems and/or frequent cough. It was validated in Chinese and widely used in primary care (Hanania et al., 2010).