Abstract: medRxiv preprint doi: https://doi.org/10.1101/2021.08.02.21260750; this version posted August 4, 2021. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. It is made available under a CC-BY-NC-ND 4.0 International license . TITLE: Hydroxychloroquine Prophylaxis against Coronavirus Disease-19: Practice Outcomes among Health-Care Workers AUTHOR: Parloop Bhatt, Vishva Patel, Prachi Shah, Keyur Parikh AFFILIATION: CARE INSTITUTE OF MEDICAL SCIENCES, SCIENCE CITY ROAD, SOLA, AHMEDABAD-380060, INDIA ABSTRACT: Background: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a rapidly emerging virus responsible for the ongoing Covid-19 pandemic with no known effective prophylaxis. We investigated whether hydroxychloroquine(HCQ) could prevent SARS CoV-2 in healthcare workers(HCW) at high-risk of exposure. Method: This voluntary observational study for the prevention and treatment of COVID-19 was conducted at a tertiary care center, from 12th June to 12th October 2020(total 16 weeks). All consented asymptomatic HCW’s of CIMS hospital were administered 400 mg HCQ twice a day on day one followed by 400 mg once weekly to be taken with meals up to 16 weeks. Data collected included OPD registration, risk assessment, medical and family history (related to COVID), physical examination and vitals, pulse oximetry, ECG (pre and post HCQ), drug adherence, side effects, adverse drug reactions. Result: The study enrolled 927 full-time, hospital-based HCWs ((including doctors, nurses, paramedical, lab technicians, sanitary workers and others), of whom 731(78.85%) initially started HCQ while 196 (21.14%) did not volunteer. The median age and weight of the study population was 27.5 years and 69.5 kg respectively. No major associated co-morbidities were present in these HCW’s. There was an increased trend towards non adherence to HCQ with each proceeding week more so after week 11. Of the 731 HCW’s taking HCQ a total of 167(22.8%) tested COVID positive at different intervals of time as against 30 HCW (15.3%) out of 196 not taking HCQ. The rate of COVID-19 positive was statistically significantly higher in the HCW’s taking HCQ (p=0.0220; 95% CI: 1.14% to 12.94%), as compared to those not on HCQ. Thus HCQ was not prophylactically effective against COVID 19 infection. No Page 1 medRxiv preprint doi: https://doi.org/10.1101/2021.08.02.21260750; this version posted August 4, 2021. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. It is made available under a CC-BY-NC-ND 4.0 International license . participants in this study experienced grade 3 or 4 adverse events. No significant difference in the median of ECG changes in QTc between pre and post HCQ administration of 46 HCW’s was observed. Conclusions: This clinical study did not detect a reduction in SARS CoV-2 transmission with prophylactic administration of 400 mg/HCQ in HCW’s. All participants who did contract SARSCoV-2 were either asymptomatic or had mild disease courses with full recoveries. All adverse events were self-limiting and no serious cardiovascular events were reported with use of HCQ. In the absence of robust data, it seems premature to recommend HCQ as a prophylactic panacea for COVID-19.