Dynamics of Conflicts on the Twitter Social Network: a case study on the use of chloroquine in Brazil Fabricio Olivetti de Franca Federal University of ABC folivetti@ufabc.edu.br Carlos da Silva dos Santos Federal University of ABC carlos.ssantos@ufabc.edu.br Claudio Luis C. Penteado Federal University of ABC claudio.penteado@ufabc.edu.br Denise Hideko Goya Federal University of ABC denise.goya@ufabc.edu.br Lucas Mazim de Sousa Federal University of ABC lucas.mazim@ufabc.edu.br Daniel Vitor B. di Genova Federal University of ABC daniel.genova@aluno.ufabc.edu.br Diogo Fornaziero S. Ramos Federal University of ABC diogo.ramos@ufabc.edu.br Carlos Alberto Kamienski Federal University of ABC carlos.kamienski@ufabc.edu.br Abstract Concerns about the advances of the COVID-19 epidemic have sparked many debates around the world. One such discussion revolved around the use of the drug called chloroquine, initially thought to be effective in reducing the mortality rate of the infection. Particularly in Brazil, even after new studies pointed to the drug’s ineffectiveness, the federal government kept the recommendation of this drug as an official treatment. The publication of an official authorization of the use of chloroquine on Twitter sparked an intense debate on social media with arguments against and in favor. This paper studies the dynamics of interactions among different user groups around this discussion, relying on network science and topic modeling analyses. Our results highlight two distinct behaviors in Twitter interaction networks, where retweets serve as positive reinforcements within information bubbles and replies act as a space of direct debate. Also, discussions are seeded by public figures, but regular users carry on the debate per se. The topic modeling analyses revealed three observable user groups in this debate: strong supporters of the Brazilian government, progressive opposition to this government, and moderate users that oppose to this specific topic but do not reject the government agenda as a whole. 1. Introduction The COVID-19 pandemic sparked many debates about vaccine development, possible treatments, and non-pharmaceutical interventions such as social distancing. Discussions soon shifted to a political sphere caused by federal and state governments’ conflicting actions such as sanitary measures, the shutdown of economic activities, and authorization for experimental treatments. One endeavor that mobilized researchers early on was the investigation of existent drugs. One such investigation was the treatment with Chloroquine (CQ) and hydroxychloroquine (HCQ). These drugs are currently used for the treatment of malaria and lupus and were candidates for such repurposing. By March 2020, early studies had revealed that CQ and HCQ could inhibit the infection of cells by SARS-CoV-2 in vitro [1], and a small observational study reported beneficial effects of HCQ for hospitalized COVID-19 patients [2]. In the United Kingdom, hydroxychloroquine was one of the drugs selected for the Randomised Evaluation of COVID-19 thERapY (RECOVERY) Trial that started enrolling patients by the end of March 2020. On March 20, 2020, the World Health Organization announced a sizeable global trial called Solidarity to test several known drugs for COVID-19 treatment, including chloroquine and hydroxychloroquine. On October 2, 2020, the website clinicaltrials.gov registered 508 studies related to hydroxychloroquine, out of 3, 507 studies about SARS-CoV-2. In the absence of any proven treatment for COVID-19, the American FDA issued emergency authorization for chloroquine and hydroxychloroquine prescription in COVID-19 cases on March 28, 2020, revoked on June 15, 2020, as evidence mounted on the ineffectiveness of these drugs and their potentially dangerous side effects [3]. On June 5, 2020, preliminary results from the RECOVERY trial were announced, showing that hydroxychloroquine did not yield beneficial effects on hospital stay duration or other outcomes and concluded that HCQ treatment was indistinguishable from standard care [4]. The hydroxychloroquine arm of the RECOVERY trial was thus halted. On July 4, 2020, the World Health Organization decided to discontinue the chloroquine arm of the Solidarity trail [5], based on interim results that showed little to no effect in reducing mortality. The issue of CQ and HCQ prescription became politicized as soon as March 2020, as USA president Donald Trump Proceedings of the 54th Hawaii International Conference on System Sciences | 2021 Page 2976 URI: https://hdl.handle.net/10125/70976 978-0-9981331-4-0 (CC BY-NC-ND 4.0)