Abstract: medRxiv preprint doi: https://doi.org/10.1101/2020.09.23.20199463; this version posted September 24, 2020. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity.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 4.0 International license . Title: Comparative Effectiveness of Famotidine in Hospitalized COVID-19 Patients short title: Famotidine and risk of COVID-19 outcomes Authors: Azza Shoaibi PhD, Stephen Fortin PharmD MS, Rachel Weinstein PhD, Jesse A. Berlin ScD, Patrick Ryan PhD Author Azza Shoaibi Email ashoaibi@its.jnj.com Position, department Associate director, observational health data analytics Stephen Fortin SFortin1@ITS.JNJ.com Manager, observational health data analytics Janssen Research & Development, LLC, Titusville, NJ, USA Rachel Weinstein RWeinst1@its.jnj.com Senior director, consumer epidemiology Janssen Research & Development, LLC, Titusville, NJ, USA Jesse Berlin JBerlin@its.jnj.com Johnson & Johnson Patrick Ryan PRyan4@its.jnj.com VP observational health data analytics VP, J&J epidemiology Affiliation Janssen Research & Development, LLC, Titusville, NJ, USA Janssen Research & Development, LLC, Titusville, NJ, USA Disclosures: AS, SF, RW, PBR are employees of Janssen Research and Development and shareholder of Johnson & Johnson, the product manufacturer of famotidine. JB is an employee and shareholder of Johnson & Johnson. Abbreviations Common Data Model Confidence interval Gastroesophageal reflux disease hazard ratios minimum detectible risk ratio Observational Health and Data Sciences and Informatics Observational Medical Outcomes Partnership Premier Hospital Database (PHD propensity score proton pump inhibitors standardized mean differences CDM CI GERD HRs MDRR OHDSI OMOP PHD PS PPI SMD Correspondence: Azza Shoaibi, MPH, PhD, 1125 Trenton-Harbourton Road, Titusville NJ, USA, 609 7302787, ashoaibi@its.jnj.com Tel: +1 Author Contributions: All authors contributed to the conceptualization and design of the study. SF authored the protocol of the study design, AS implemented the statistical analysis, RW, PBR and JB reviewed and approved the study diagnostics and results. AS drafted the manuscript and all coauthors reviewed and contributed to the manuscript writing. NOTE: This preprint reports new research that has not been certified by peer review and should not be used to guide clinical practice. medRxiv preprint doi: https://doi.org/10.1101/2020.09.23.20199463; this version posted September 24, 2020. 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 4.0 International license . Abstract (260 words): Background: Famotidine has been posited as a potential treatment for COVID-19. We compared the incidence of COVID-19 outcomes (i.e., death; and death or intensive services use) among hospitalized famotidine users vs. proton pump inhibitors (PPIs) users, hydroxychloroquine users or famotidine nonusers separately. Methods: We constructed a retrospective cohort study using data from COVID-19 Premier Hospital electronic health records. Study population were COVID-19 hospitalized patients aged 18 years or older. Famotidine, PPI and hydroxychloroquine exposure groups were defined as patients dispensed any medication containing one of..