A Randomized Trial of Hydroxychloroquine as Postexposure Prophylaxis for Covid-19.

BACKGROUND: Coronavirus disease 2019 (Covid-19) occurs after exposure to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). For persons who are exposed, the standard of care is observation and quarantine. Whether hydroxychloroquine can prevent symptomatic infection after SARS-CoV-2 exposure is unknown. METHODS: We conducted a randomized, double-blind, placebo-controlled trial across the United States and parts of Canada testing hydroxychloroquine as postexposure prophylaxis. We enrolled adults who had household or occupational exposure to someone with confirmed Covid-19 at a distance of less than 6 ft for more than 10 minutes while wearing neither a face mask nor an eye shield (high-risk exposure) or while wearing a face mask but no eye shield (moderate-risk exposure). Within 4 days after exposure, we randomly assigned participants to receive either placebo or hydroxychloroquine (800 mg once, followed by 600 mg in 6 to 8 hours, then 600 mg daily for 4 additional days). The primary outcome was the incidence of either laboratory-confirmed Covid-19 or illness compatible with Covid-19 within 14 days. RESULTS: We enrolled 821 asymptomatic participants. Overall, 87.6% of the participants (719 of 821) reported a high-risk exposure to a confirmed Covid-19 contact. The incidence of new illness compatible with Covid-19 did not differ significantly between participants receiving hydroxychloroquine (49 of 414 [11.8%]) and those receiving placebo (58 of 407 [14.3%]); the absolute difference was -2.4 percentage points (95% confidence interval, -7.0 to 2.2; P = 0.35). Side effects were more common with hydroxychloroquine than with placebo (40.1% vs. 16.8%), but no serious adverse reactions were reported. CONCLUSIONS: After high-risk or moderate-risk exposure to Covid-19, hydroxychloroquine did not prevent illness compatible with Covid-19 or confirmed infection when used as postexposure prophylaxis within 4 days after exposure. (Funded by David Baszucki and Jan Ellison Baszucki and others; ClinicalTrials.gov number, NCT04308668.).

Hydroxychloroquine as Pre-exposure Prophylaxis for Coronavirus Disease 2019 (COVID-19) in Healthcare Workers: A Randomized Trial.

BACKGROUND: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a rapidly emerging virus causing the ongoing coronavirus disease 2019 (COVID-19) pandemic with no known effective prophylaxis. We investigated whether hydroxychloroquine could prevent SARS-CoV-2 in healthcare workers at high risk of exposure. METHODS: We conducted a randomized, double-blind, placebo-controlled clinical trial of healthcare workers with ongoing exposure to persons with SARS-CoV-2, including those working in emergency departments, intensive care units, COVID-19 hospital wards, and first responders. Participants across the United States and in the Canadian province of Manitoba were randomized to hydroxychloroquine loading dose then 400 mg once or twice weekly for 12 weeks. The primary endpoint was confirmed or probable COVID-19-compatible illness. We measured hydroxychloroquine whole-blood concentrations. RESULTS: We enrolled 1483 healthcare workers, of whom 79% reported performing aerosol-generating procedures. The incidence of COVID-19 (laboratory-confirmed or symptomatic compatible illness) was 0.27 events/person-year with once-weekly and 0.28 events/person-year with twice-weekly hydroxychloroquine compared with 0.38 events/person-year with placebo. For once-weekly hydroxychloroquine prophylaxis, the hazard ratio was .72 (95% CI, .44-1.16; P = .18) and for twice-weekly was .74 (95% CI, .46-1.19; P = .22) compared with placebo. Median hydroxychloroquine concentrations in whole blood were 98 ng/mL (IQR, 82-120) with once-weekly and 200 ng/mL (IQR, 159-258) with twice-weekly dosing. Hydroxychloroquine concentrations did not differ between participants who developed COVID-19-compatible illness (154 ng/mL) versus participants without COVID-19 (133 ng/mL; P = .08). CONCLUSIONS: Pre-exposure prophylaxis with hydroxychloroquine once or twice weekly did not significantly reduce laboratory-confirmed COVID-19 or COVID-19-compatible illness among healthcare workers. CLINICAL TRIALS REGISTRATION: Clinicaltrials.gov NCT04328467.

Hydroxychloroquine in Nonhospitalized Adults With Early COVID-19 : A Randomized Trial.

BACKGROUND: No effective oral therapy exists for early coronavirus disease 2019 (COVID-19). OBJECTIVE: To investigate whether hydroxychloroquine could reduce COVID-19 severity in adult outpatients. DESIGN: Randomized, double-blind, placebo-controlled trial conducted from 22 March through 20 May 2020. (ClinicalTrials.gov: NCT04308668). SETTING: Internet-based trial across the United States and Canada (40 states and 3 provinces). PARTICIPANTS: Symptomatic, nonhospitalized adults with laboratory-confirmed COVID-19 or probable COVID-19 and high-risk exposure within 4 days of symptom onset. INTERVENTION: Oral hydroxychloroquine (800 mg once, followed by 600 mg in 6 to 8 hours, then 600 mg daily for 4 more days) or masked placebo. MEASUREMENTS: Symptoms and severity at baseline and then at days 3, 5, 10, and 14 using a 10-point visual analogue scale. The primary end point was change in overall symptom severity over 14 days. RESULTS: Of 491 patients randomly assigned to a group, 423 contributed primary end point data. Of these, 341 (81%) had laboratory-confirmed infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) or epidemiologically linked exposure to a person with laboratory-confirmed infection; 56% (236 of 423) were enrolled within 1 day of symptoms starting. Change in symptom severity over 14 days did not differ between the hydroxychloroquine and placebo groups (difference in symptom severity: relative, 12%; absolute, -0.27 point [95% CI, -0.61 to 0.07 point]; P = 0.117). At 14 days, 24% (49 of 201) of participants receiving hydroxychloroquine had ongoing symptoms compared with 30% (59 of 194) receiving placebo (P = 0.21). Medication adverse effects occurred in 43% (92 of 212) of participants receiving hydroxychloroquine versus 22% (46 of 211) receiving placebo (P < 0.001). With placebo, 10 hospitalizations occurred (2 non-COVID-19-related), including 1 hospitalized death. With hydroxychloroquine, 4 hospitalizations occurred plus 1 nonhospitalized death (P = 0.29). LIMITATION: Only 58% of participants received SARS-CoV-2 testing because of severe U.S. testing shortages. CONCLUSION: Hydroxychloroquine did not substantially reduce symptom severity in outpatients with early, mild COVID-19. PRIMARY FUNDING SOURCE: Private donors.

The bacterial type III-secreted protein AvrRps4 is a bipartite effector.

Bacterial effector proteins secreted into host plant cells manipulate those cells to the benefit of the pathogen, but effector-triggered immunity (ETI) occurs when effectors are recognized by host resistance proteins. The RPS4/RRS1 pair recognizes the Pseudomonas syringae pv. pisi effector AvrRps4. AvrRps4 is processed in planta into AvrRps4N (133 amino acids), homologous to the N-termini of other effectors including the native P. syringae pv. tomato strain DC3000 effector HopK1, and AvrRps4C (88 amino acids). Previous data suggested that AvrRps4C alone is necessary and sufficient for resistance when overexpressed in heterologous systems. We show that delivering AvrRps4C from DC3000, but not from a DC3000 hopK1- strain, triggers resistance in the Arabidopsis accession Col-0. Delivering AvrRps4C in tandem with AvrRps4N, or as a chimera with HopK1N, fully complements AvrRps4-triggered immunity. AvrRps4N in the absence of AvrRps4C enhances virulence in Col-0. In addition, AvrRps4N triggers a hypersensitive response in lettuce that is attenuated by coexpression of AvrRps4C, further supporting the role of AvrRps4N as a bona fide effector domain. Based on these results we propose that evolutionarily, fusion of AvrRps4C to AvrRps4N may have counteracted recognition of AvrRps4N, and that the plant RPS4/RRS1 resistance gene pair was selected as a countermeasure. We conclude that AvrRps4 represents an unusual chimeric effector, with recognition in Arabidopsis by RPS4/RRS1 requiring the presence of both processed effector moieties.

Post-exposure prophylaxis or pre-emptive therapy for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2): study protocol for a pragmatic randomized-controlled trial.

BACKGROUND: The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) emerged in December 2019 causing the coronavirus disease (COVID-19) pandemic. Currently, there is a lack of evidence-based therapies to prevent COVID-19 following exposure to the virus, or to prevent worsening of symptoms following confirmed infection. We describe the design of a clinical trial of hydroxychloroquine for post-exposure prophylaxis (PEP) and pre-emptive therapy (PET) for COVID-19. METHODS: We will conduct two nested multicentre international double-blind randomized placebo-controlled clinical trials of hydroxychloroquine for: 1) PEP of asymptomatic household contacts or healthcare workers exposed to COVID-19 within the past four days, and 2) PET for symptomatic outpatients with COVID-19 showing symptoms for less than four days. We will recruit 1,500 patients each for the PEP and PET trials. Participants will be randomized 1:1 to receive five days of hydroxychloroquine or placebo. The primary PEP trial outcome will be the incidence of symptomatic COVID-19. The primary PET trial outcome will be an ordinal scale of disease severity (not hospitalized, hospitalized without intensive care, hospitalization with intensive care, or death). Participant screening, informed consent, and follow-up will be exclusively internet-based with appropriate regulatory and research ethics board approvals in Canada and the United States. DISCUSSION: These complementary randomized-controlled trials are innovatively designed and adequately powered to rapidly answer urgent questions regarding the effectiveness of hydroxychloroquine to reduce virus transmission and disease severity of COVID-19 during a pandemic. In-person participant follow-up will not be conducted to facilitate social distancing strategies and reduce risks of exposure to study personnel. Innovative trial approaches are needed to urgently assess therapeutic options to mitigate the global impact of this pandemic. TRIALS REGISTRATION: clinicaltrials.gov (NCT04308668); registered 16 March, 2020.

RéSUMé: CONTEXTE: Le syndrome respiratoire aigu sévère du coronavirus 2 (SARS-CoV-2) est apparu en décembre 2019, provoquant la pandémie de la COVID-19. À l'heure actuelle, il n'existe aucun traitement fondé sur des données probantes permettant de prévenir la COVID-19 suite à une exposition au virus ou de prévenir l'aggravation des symptômes suite à une infection confirmée. Nous décrivons la conception d'une étude clinique examinant l'utilisation d'hydroxychloroquine en tant que prophylaxie post-exposition (PPE) et de traitement préventif (TP) pour la COVID-19. MéTHODE: Nous réaliserons deux études cliniques imbriquées contrôlées par placebo, randomisées, à double insu, internationales et multicentriques examinant l'utilisation d'hydroxychloroquine pour : 1) la prophylaxie post-exposition des contacts asymptomatiques dans un même foyer ou les travailleurs de la santé exposés à la COVID-19 au cours des quatre derniers jours, et 2) le traitement préventif des patients symptomatiques en ambulatoire atteints de COVID-19 et présentant des symptômes pour une durée totale de moins de quatre jours. Nous recruterons 1500 patients pour chaque bras de l'étude (PPE et TP). Les participants seront randomisés à un ratio de 1 : 1 pour recevoir cinq jours d'hydroxychloroquine ou de placebo. Le critère d'évaluation principal de l'étude PPE sera l'incidence de COVID-19 symptomatique. Le critère d'évaluation principal de l'étude TP consistera en une échelle ordinale de la gravité de la maladie (pas d'hospitalisation, hospitalisation sans soins intensifs, hospitalisation avec soins intensifs, ou décès). La sélection des participants, le consentement éclairé et le suivi se feront exclusivement en ligne après avoir obtenu les consentements réglementaires et des comités d'éthique de la recherche appropriés au Canada et aux États-Unis. DISCUSSION: Ces études randomisées contrôlées complémentaires sont conçues de façon innovatrice et disposent de la puissance nécessaire pour répondre rapidement aux questions urgentes quant à l'efficacité de l'hydroxychloroquine pour réduire la transmission et la gravité de la maladie de la COVID-19 pendant une pandémie. Le suivi des participants ne sera pas réalisé en personne afin de faciliter les stratégies de distanciation sociale et de réduire le risque d'exposition du personnel de l'étude. Des approches innovatrices d'études sont nécessaires afin d'évaluer rapidement les options thérapeutiques pour mitiger l'impact global de cette pandémie. ENREGISTREMENT DE L'éTUDE: clinicaltrials.gov (NCT04308668); enregistrées le 16 mars 2020.

Correlation between Blood and CSF Compartment Cytokines and Chemokines in Subjects with Cryptococcal Meningitis.

BACKGROUND: Though peripheral blood is a crucial sample to study immunology, it is unclear whether the immune environment in the peripheral vasculature correlates with that at the end-organ site of infection. Using cryptococcal meningitis as a model, we investigated the correlation between serum and cerebrospinal fluid biomarkers over time. METHODS: We analyzed the cerebrospinal fluid and serum of 160 subjects presenting with first episode cryptococcal meningitis for soluble cytokines and chemokines measured by Luminex assay. Specimens were collected at meningitis diagnosis, 1-week, and 2-week post cryptococcal diagnosis. We compared paired samples by Spearman's correlation and the p value was set at <0.01. RESULTS: Of the 21 analytes tested at baseline, there was no correlation detected between nearly all analytes. A weak negative correlation was found between serum and cerebrospinal fluid levels of interferon-gamma (Rho = -0.214; p = .007) and interleukin-4 (Rho = -0.232; p = .003). There was no correlation at 1-week post cryptococcal diagnosis. However, at 2-week post cryptococcal diagnosis, there was a weak positive correlation of granulocyte-macrophage colony-stimulating factor levels (Rho = 0.25; p = .007) in serum and cerebrospinal fluid. No cytokine or chemokine showed consistent correlation overtime. CONCLUSION: Based on our analysis of 21 biomarkers, serum and cerebrospinal fluid immune responses do not correlate. There appears to be a distinct immune environment in terms of soluble biomarkers in the vasculature versus end-organ site of infection. While this is a model of HIV-related cryptococcal meningitis, we postulate that assuming the blood compartment is representative of the immune function at the end-organ site of infection may not be appropriate.

Lessons Learned From Conducting Internet-Based Randomized Clinical Trials During a Global Pandemic.

As the severe acute respiratory syndrome coronavirus 2 pandemic evolved, it was apparent that well designed and rapidly conducted randomized clinical trials were urgently needed. However, traditional clinical trial design presented several challenges. Notably, disease prevalence initially varied by time and region, and the pockets of outbreaks evolved geographically over time. Coupled with an occupational hazard from in-person study visits, timely recruitment would prove difficult in a traditional in-person clinical trial. Thus, our team opted to launch nationwide internet-based clinical trials using patient-reported outcome measures. In total, 2795 participants were recruited using traditional and social media, with screening and enrollment performed via an online data capture system. Follow-up surveys and survey reminders were similarly managed through this online system with manual participant outreach in the event of missing data. In this report, we present a narrative of our experience running internet-based clinical trials and provide recommendations for the design of future clinical trials during a world pandemic.

Feasibility of SARS-CoV-2 Antibody Testing in Remote Outpatient Trials.

Background: During the coronavirus disease 2019 (COVID-19) pandemic, clinical trials necessitated rapid testing to be performed remotely. Dried blood spot (DBS) techniques have enabled remote HIV virologic testing globally, and more recently, antibody testing as well. We evaluated DBS testing for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibody testing in outpatients to assess seropositivity. Methods: In 2020, we conducted 3 internet-based randomized clinical trials and offered serologic testing via self-collected DBS as a voluntary substudy. COVID-19 diagnosis was based on the Centers for Disease Control and Prevention case definition with epidemiological link to cases. A minority reported polymerase chain reaction (PCR) testing at an outside facility. We tested for anti-SARS-CoV-2 immunoglobulin via antibody detection by agglutination-PCR (ADAP) and compared the results with enzyme-linked immunosorbent assay (ELISA). Results: Of 2727 participants in the primary studies, 60% (1648/2727) consented for serology testing; 56% (931/1648) returned a usable DBS sample. Of those who were asymptomatic, 5% (33/707) had positive ADAP serology. Of participants with a positive PCR, 67% (36/54) had positive SARS-CoV-2 antibodies. None of those who were PCR-positive and asymptomatic were seropositive (0/7). Of 77 specimens tested for concordance via ELISA, 83% (64/77) were concordant. The challenges of completing a remote testing program during a pandemic included sourcing and assembling collection kits, delivery and return of the kits, and troubleshooting testing. Self-collection was successful for >95% of participants. Delays in US mail with possible sample degradation and timing of DBS collection complicated the analysis. Conclusions: We found remote antibody testing during a global pandemic feasible although challenging. We identified an association between symptomatic COVID-19 and positive antibody results at a similar prevalence as other outpatient cohorts.

Symptoms of COVID-19 Outpatients in the United States.

BACKGROUND: Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) is a novel pathogen causing the current worldwide coronavirus disease 2019 (COVID-19) pandemic. Due to insufficient diagnostic testing in the United States, there is a need for clinical decision-making algorithms to guide testing prioritization. METHODS: We recruited participants nationwide for a randomized clinical trial. We categorized participants into 3 groups: (1) those with confirmed SARS-CoV-2 infection, (2) those with probable SARS-CoV-2 infection (pending test or not tested but with a confirmed COVID-19 contact), and (3) those with possible SARS-CoV-2 infection (pending test or not tested and with a contact for whom testing was pending or not performed). We compared the frequency of self-reported symptoms in each group and categorized those reporting symptoms in early infection (0-2 days), midinfection (3-5 days), and late infection (>5 days). RESULTS: Among 1252 symptomatic persons screened, 316 had confirmed, 393 had probable, and 543 had possible SARS-CoV-2 infection. In early infection, those with confirmed and probable SARS-CoV-2 infection shared similar symptom profiles, with fever most likely in confirmed cases (P = .002). Confirmed cases did not show any statistically significant differences compared with unconfirmed cases in symptom frequency at any time point. The most commonly reported symptoms in those with confirmed infection were cough (82%), fever (67%), fatigue (62%), and headache (60%), with only 52% reporting both fever and cough. CONCLUSIONS: Symptomatic persons with probable SARS-CoV-2 infection present similarly to those with confirmed SARS-CoV-2 infection. There was no pattern of symptom frequency over time.

Review: Hydroxychloroquine and Chloroquine for Treatment of SARS-CoV-2 (COVID-19).

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a rapidly emerging viral infection causing coronavirus disease 2019 (COVID-19). Hydroxychloroquine and chloroquine have garnered unprecedented attention as potential therapeutic agents against COVID-19 following several small clinical trials, uncontrolled case series, and public figure endorsements. While there is a growing body of scientific data, there is also concern for harm, particularly QTc prolongation and cardiac arrhythmias. Here, we perform a rapid narrative review and discuss the strengths and limitations of existing in vitro and clinical studies. We call for additional randomized controlled trial evidence prior to the widespread incorporation of hydroxychloroquine and chloroquine into national and international treatment guidelines.

Hydroxychloroquine as pre-exposure prophylaxis for COVID-19 in healthcare workers: a randomized trial.

BACKGROUND: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a rapidly emerging virus causing the ongoing Covid-19 pandemic with no known effective prophylaxis. We investigated whether hydroxychloroquine could prevent SARS CoV-2 in healthcare workers at high-risk of exposure. METHODS: We conducted a randomized, double-blind, placebo-controlled clinical trial of healthcare workers with ongoing exposure to persons with Covid-19, including those working in emergency departments, intensive care units, Covid-19 hospital wards, and first responders. Participants across the United States and in the Canadian province of Manitoba were randomized to hydroxychloroquine 400mg once weekly or twice weekly for 12 weeks. The primary endpoint was confirmed or probable Covid-19-compatible illness. We measured hydroxychloroquine whole blood concentrations. RESULTS: We enrolled 1483 healthcare workers, of which 79% reported performing aerosol-generating procedures. The incidence of Covid-19 (laboratory-confirmed or symptomatic compatible illness) was 0.27 events per person-year with once-weekly and 0.28 events per person-year with twice-weekly hydroxychloroquine compared with 0.38 events per person-year with placebo. For once weekly hydroxychloroquine prophylaxis, the hazard ratio was 0.72 (95%CI 0.44 to 1.16; P=0.18) and for twice weekly was 0.74 (95%CI 0.46 to 1.19; P=0.22) as compared with placebo. Median hydroxychloroquine concentrations in whole blood were 98 ng/mL (IQR, 82-120) with once-weekly and 200 ng/mL (IQR, 159-258) with twice-weekly dosing. Hydroxychloroquine concentrations did not differ between participants who developed Covid-19 (154 ng/mL) versus participants without Covid-19 (133 ng/mL; P=0.08). CONCLUSIONS: Pre-exposure prophylaxis with hydroxychloroquine once or twice weekly did not significantly reduce laboratory-confirmed Covid-19 or Covid-19-compatible illness among healthcare workers.

Safety of Hydroxychloroquine among Outpatient Clinical Trial Participants for COVID-19.

INTRODUCTION: Use of hydroxychloroquine in hospitalized patients with COVID-19, especially in combination with azithromycin, has raised safety concerns. Here, we report safety data from three outpatient randomized clinical trials. METHODS: We conducted three randomized, double-blind, placebo-controlled trials investigating hydroxychloroquine as pre-exposure prophylaxis, post-exposure prophylaxis and early treatment for COVID-19. We excluded individuals with contraindications to hydroxychloroquine. We collected side effects and serious adverse events. We report descriptive analyses of our findings. RESULTS: We enrolled 2,795 participants. The median age of research participants was 40 (IQR 34-49) years, and 59% (1633/2767) reported no chronic medical conditions. Overall 2,324 (84%) participants reported side effect data, and 638 (27%) reported at least one medication side effect. Side effects were reported in 29% with daily, 36% with twice weekly, 31% with once weekly hydroxychloroquine compared to 19% with placebo. The most common side effects were upset stomach or nausea (25% with daily, 18% with twice weekly, 16% with weekly, vs. 10% for placebo), followed by diarrhea, vomiting, or abdominal pain (23% for daily, 16% twice weekly, 12% weekly, vs. 6% for placebo). Two individuals were hospitalized for atrial arrhythmias, one on placebo and one on twice weekly hydroxychloroquine. No sudden deaths occurred. CONCLUSION: Data from three outpatient COVID-19 trials demonstrated that gastrointestinal side effects were common but mild with the use of hydroxychloroquine, while serious side effects were rare. No deaths occurred related to hydroxychloroquine. Randomized clinical trials can safely investigate whether hydroxychloroquine is efficacious for COVID-19.

Safety of Hydroxychloroquine Among Outpatient Clinical Trial Participants for COVID-19.

BACKGROUND: Use of hydroxychloroquine in hospitalized patients with coronavirus disease 2019 (COVID-19), especially in combination with azithromycin, has raised safety concerns. Here, we report safety data from 3 outpatient randomized clinical trials. METHODS: We conducted 3 randomized, double-blind, placebo-controlled trials investigating hydroxychloroquine as pre-exposure prophylaxis, postexposure prophylaxis, and early treatment for COVID-19 using an internet-based design. We excluded individuals with contraindications to hydroxychloroquine. We collected side effects and serious adverse events. We report descriptive analyses of our findings. RESULTS: We enrolled 2795 participants. The median age of research participants (interquartile range) was 40 (34-49) years, and 59% (1633/2767) reported no chronic medical conditions. Overall 2544 (91%) participants reported side effect data, and 748 (29%) reported at least 1 medication side effect. Side effects were reported in 40% with once-daily, 36% with twice-weekly, 31% with once-weekly hydroxychloroquine, compared with 19% with placebo. The most common side effects were upset stomach or nausea (25% with once-daily, 19% with twice-weekly, and 18% with once-weekly hydroxychloroquine, vs 11% for placebo), followed by diarrhea, vomiting, or abdominal pain (23% for once-daily, 17% twice-weekly, and 13% once-weekly hydroxychloroquine, vs 7% for placebo). Two individuals were hospitalized for atrial arrhythmias, 1 on placebo and 1 on twice-weekly hydroxychloroquine. No sudden deaths occurred. CONCLUSIONS: Data from 3 outpatient COVID-19 trials demonstrated that gastrointestinal side effects were common but mild with the use of hydroxychloroquine, while serious side effects were rare. No deaths occurred related to hydroxychloroquine. Randomized clinical trials, in cohorts of healthy outpatients, can safely investigate whether hydroxychloroquine is efficacious for COVID-19. CLINICALTRIALSGOV IDENTIFIER: NCT04308668 for postexposure prophylaxis and early treatment trials; NCT04328467 for pre-exposure prophylaxis trial.