This was a single-centre, prospective, randomised controlled cohort study with 447 individuals. All patients tested positive for COVID-19 with a PCR test, and were admitted into the hospital between March 7 and July 8, 2020. Most of the patients were given only the recommended treatment protocol of hydroxychloroquine and/or favipiravir. 52/447 randomly chosen patients with at least one chronic disease and moderate-to-severe respiratory symptoms were given in addition to the standard regimen, the quercetin (1000mg), vitamin C (1000mg), bromelain (100mg) supplementation daily.