key: cord-0975874-dt7hip0z
authors: Rajasingham, Radha; Bangdiwala, Ananta S; Nicol, Melanie R; Skipper, Caleb P; Pastick, Katelyn A; Axelrod, Margaret L; Pullen, Matthew F; Nascene, Alanna A; Williams, Darlisha A; Engen, Nicole W; Okafor, Elizabeth C; Rini, Brian I; Mayer, Ingrid A; McDonald, Emily G; Lee, Todd C; Li, Peter; MacKenzie, Lauren J; Balko, Justin M; Dunlop, Stephen J; Hullsiek, Katherine H; Boulware, David R; Lofgren, Sarah M
title: Hydroxychloroquine as pre-exposure prophylaxis for COVID-19 in healthcare workers: a randomized trial
date: 2020-10-17
journal: Clin Infect Dis
DOI: 10.1093/cid/ciaa1571
sha: 8c59bb1827cac06b6d39aca714c1506afbb7ab06
doc_id: 975874
cord_uid: dt7hip0z

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 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 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-compatible illness (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.

A c c e p t e d M a n u s c r i p t Background Covid-19 creates a substantial strain on the healthcare system with frontline healthcare workers at increased risk of infection, and yet they are simultaneously essential for sustaining an adequate emergency response. Unfortunately, at present, no effective oral chemoprophylaxis or vaccination against Covid-19 exists. On October 7, 2020, the Centers for Disease Control and Prevention (CDC) reported over 173,000 cases of Covid-19 among healthcare personnel in the United States [1] . An effective pre-exposure prophylaxis medication for healthcare workers with repeated SARS CoV-2 exposure, even if only partially effective, would be a powerful public health tool to reduce transmission of SARS-CoV-2 and protect frontline workers from Covid-19 [2] .

While intensive efforts are being directed towards treatment discovery and vaccine development, repurposing existing medications is a more swift and economical approach to fulfill a time-sensitive need for effective prophylaxis. Chloroquine has demonstrated in vitro activity against SARS-CoV and SARS-CoV-2 [3, 4] . Recent studies demonstrated that hydroxychloroquine, a derivative molecule of chloroquine, is also active against SARS-CoV-2 and may demonstrate greater in vitro viral inhibition [5, 6] . However, it remains unclear if in vitro activity corresponds to clinical efficacy. Randomized clinical trials in post-exposure prophylaxis, early outpatient treatment, and inpatient treatment have not borne out this initial promise [7] [8] [9] [10] . Nonetheless, some have postulated that the post-exposure and early treatment trials may not have achieved therapeutic concentrations early enough to have demonstrated a benefit [7] . In India, hydroxychloroquine 400mg weekly is recommended nationally in A c c e p t e d M a n u s c r i p t asymptomatic healthcare workers at high risk for Covid-19, despite no substantial evidence that it prevents Covid-19 [11] .

There is ongoing interest in the concept of pre-exposure prophylaxis whereby a patient has already achieved adequate drug concentrations at the time of viral exposure. Therefore, we sought to determine the effectiveness of hydroxychloroquine as pre-exposure prophylaxis in healthcare workers at high-risk of SARS-CoV-2 exposure in a randomized, placebo-controlled clinical trial setting.

We conducted a randomized, double-blind, placebo-controlled clinical trial (Clinicaltrials.gov NCT04328467) to evaluate whether hydroxychloroquine could prevent Covid-19 in high-risk healthcare workers across the United States and Canada. Enrollment began on April 6, 2020, and ended May 26, 2020; follow up was completed on July 13, 2020.

Participants were randomly assigned in a 2:2:1:1 ratio to receive hydroxychloroquine given as a loading dose of 400mg (two 200mg tablets) twice separated by 6-8 hours followed by (i) 400 mg (two 200mg tablets) once weekly for 12 weeks or (ii) 400 mg (two 200mg tablets) twice weekly for 12 weeks, or to placebo which was prescribed in a matched fashion including a loading dose of two tablets followed by two tablets once or twice weekly for 12 weeks.

We included healthcare workers aged 18 years and older with ongoing exposure to persons with Covid-19. A high-risk healthcare worker was defined as working in an emergency A c c e p t e d M a n u s c r i p t department or intensive care unit, on a dedicated Covid-19 hospital ward, as a first responder, or whose job description included regularly performing aerosol-generating procedures (e.g., anesthesiologists or otolaryngologists), and included physicians, nurses, advanced practice providers, and other personnel (e.g., respiratory therapists).

We excluded persons who reported active or prior Covid-19 (either confirmed or symptom-compatible illness), no expected exposure to patients, or contraindication to hydroxychloroquine (Appendix).

We enrolled participants nationwide in the United States and the Canadian province of Manitoba. We recruited participants using social media platforms targeting healthcare providers.

Participants self-enrolled via a secure internet-based survey using the Research Electronic Data Capture (REDCap) system [12] . Participants provided a digitally captured informed consent signature after passing a comprehension assessment.

Online study assessments were scheduled at enrollment, medication initiation, and weekly after enrollment. Each assessment included a report of study medication adherence, medication side effects, the number of patient-facing contact hours, contact with patients with The definition of Covid-19-compatible symptoms was based on guidance from the US Council for State and Territorial Epidemiologists (Appendix) [13] . Specifically, probable disease was defined as having cough, shortness of breath, or difficulty breathing, OR two or more of the following symptoms: fevers, chills, rigors, myalgia, headache, sore throat, new olfactory and taste disorders. Possible disease was defined as one or more COVID-19-compatible symptoms.

Three blinded infectious diseases physicians independently adjudicated cases of symptomatic participants based on the above criteria.

Secondary outcomes included incidence of confirmed SARS-CoV-2 detection, incidence of possible Covid-19, and incidence of hospitalization, death, or other adverse events. Study medication adherence and side effects were all collected through weekly self-reported surveys.

Participants were sequentially randomized at the research pharmacies. Treatment assignments were concealed from investigators and participants. Blinded hydroxychloroquine or placebo (folic acid) was dispensed and a 12 week supply shipped to participants by courier.

A c c e p t e d M a n u s c r i p t

The trial was designed anticipating a 10% event rate of Covid-19 in high-risk healthcare workers over 12 weeks. Using Log-rank testing with a 50% relative effect size to reduce new symptomatic infections, a two-sided alpha of 0.025 and 80% power, an estimated 1050 participants per arm were required. The trial was powered at  = 0.025 to account for the two treatment dosing regimens versus placebo comparisons.

We compared the incidence of Covid-19-free survival using the Log-rank test and estimated hazard ratios using a Cox proportional hazards model. We compared secondary endpoints of proportions by Fisher's exact test. We conducted analyses with SAS software version 9.4 (SAS Institute), according to the intention-to-treat principle. Participants were righthand censored at time of last contact for those not completing 12 weeks of follow up. As prespecified, participants who developed Covid-19-compatible illness (i.e., primary endpoint) prior to initiating the study medicine were excluded from the primary analysis.

A prespecified subgroup analysis was performed to investigate whether hydroxychloroquine drug concentrations correlated with protection from Covid-19. Whole blood was self-collected from participants who consented using Neoteryx® volumetric absorbed microsampling kits (Neoteryx, Torrance, CA) at least four weeks after study medication initiation. Hydroxychloroquine concentrations were quantified similarly to methods previously A c c e p t e d M a n u s c r i p t published (Appendix) [14] . The Wilcoxon rank-sum test compared trough concentrations between participants who developed Covid-19 and those who did not.

An independent DSMB reviewed the data after 25% of participants had completed four weeks of follow up. Stopping guidelines were provided to the DSMB via a Lan-DeMets spending function analog of the O'Brien-Fleming boundaries for the primary outcome.

Before the first interim analysis on May 21, 2020, it became apparent that we would not meet our initial enrollment goal of 3150 participants (Figure S2 ). At the first interim analysis, and without unblinding of treatment allocation, the principal investigator proposed to the data safety monitoring board stopping enrollment due to an inability to recruit participants, with continued follow up for those already enrolled. Enrollment was stopped on May 26, 2020, and outcomes data were collected through July 13, 2020.

Of 2271 persons screened, 1483 high-risk healthcare workers from the United States and Canada were enrolled with: 494 randomized to once-weekly hydroxychloroquine, 495 randomized to twice-weekly hydroxychloroquine, and 494 randomized to placebo (Figure 1) . 

The study accrued 311 person-years of follow up, and 97 participants (6.5%) developed Covid-19 (either PCR confirmed or symptomatically compatible illness) during the trial. Overall, confirmed or probable Covid-19-compatible illness occurred in 29 (5.9%) receiving once-weekly hydroxychloroquine, 29 (5.9%) receiving twice-weekly hydroxychloroquine, and 39 (7.9%) receiving placebo. The corresponding incidence of Covid-19 or compatible illness was 0.27 and 0.28 events per person-year for those taking hydroxychloroquine once or twice weekly, respectively, as compared to 0.38 events per person-year in those receiving placebo ( Table 2) . Table 2) .

Self-reported adherence to study medicine was not significantly different by treatment group (Figure S9) . Of those who reported full adherence at >80% of surveys, Covid-19 occurred Side effects were reported in 21% (100 of 469) of participants assigned to placebo (Table   S4 ), 31% (148 of 473; P<0.001) in the once-weekly hydroxychloroquine group, and 36% (168 of 463; P<0.001) in the twice-weekly hydroxychloroquine group. The most common side effect was stomach upset and nausea (placebo 12.2%, hydroxychloroquine once-weekly 17.5%, and hydroxychloroquine twice-weekly 19.4%), followed by gastrointestinal disturbance and diarrhea (placebo 7.5%, hydroxychloroquine once-weekly 12.9%, and hydroxychloroquine twice-weekly

A c c e p t e d M a n u s c r i p t

Twenty hospitalizations occurred during the study: nine in the placebo arm, three in the hydroxychloroquine once-weekly arm, and eight in the hydroxychloroquine twice-weekly arm.

Reasons for hospitalization are summarized in the Appendix. Two hospitalizations were related to Covid-19 (1 placebo, 1 twice-weekly group). One person in the placebo group was hospitalized twice for new atrial fibrillation, and one person in the hydroxychloroquine twiceweekly arm was hospitalized for syncope and new supraventricular tachycardiaa possible hydroxychloroquine-related serious adverse event (SAE). No intensive care unit stays or deaths occurred.

In prespecified subgroup analyses, there were no significant differences in treatment efficacy (Appendix).

Hydroxychloroquine concentrations were measured in dried whole blood from 180 participants in the hydroxychloroquine groups of whom 18 were confirmed or probable Covid-19 and 6 were considered possible Covid-19 (Table S7) (Figure 3) . To exclude surreptitious crossovers, we measured hydroxychloroquine A c c e p t e d M a n u s c r i p t concentrations in 49 participants (10%) randomized to placebo, and all were below the limit of quantification of 50 ng/mL.

In this randomized, double-blind, placebo-controlled trial evaluating hydroxychloroquine as pre-exposure prophylaxis for Covid-19 in high-risk healthcare workers, we found no statistically significant reduction in Covid-19 incidence in those receiving 400mg weekly or twice weekly hydroxychloroquine when compared with placebo. Reasons for no effect observed may be due to hydroxychloroquine concentrations being too low, or because hydroxychloroquine is ineffective against Covid-19 in vivo [15] .

Nonetheless, we observed no difference in hydroxychloroquine concentrations between those who reported Covid-19 symptomatically compatible illness and those who did not, in a subsample of trial participants. Similarly, an animal model of macaques showed that hydroxychloroquine offered no protection against SARS-CoV-2 acquisition when given as preexposure prophylaxis [15] . While there are no validated therapeutic target concentrations of hydroxychloroquine for protection against Covid-19, we chose dosing regimens predicted to achieve plasma concentrations above the in vitro EC 50 [16] . Assuming blood concentrations are seven-fold higher than plasma [17] , no participants had plasma troughs higher than reported in vitro EC 50. Plasma concentrations of 235 ng/mL (~0.7µM) would extrapolate to a whole blood target >1600 ng/mL, significantly higher than troughs achieved in our study. The discrepancy between our simulated and observed concentrations is consistent with a recent analysis [18] , which suggested that due to sequestering of drug in whole blood leukocytes and platelets not adequately removed during processing, the pharmacokinetic parameters upon which we based A c c e p t e d M a n u s c r i p t our simulations may have overestimated plasma concentrations [19] . This finding is likely applicable to all hydroxychloroquine trials. Notably, our whole blood troughs suggest that even with daily dosing, extrapolated plasma trough concentrations above EC 50 are unlikely. Ongoing trials investigating the efficacy of daily dosing should consider obtaining plasma concentrations to further decipher whether daily dosing is adequate, and in the context of appropriate dosing, if hydroxychloroquine is effective at preventing SARS CoV-2 infection. In one randomized trial of 125 participants, daily hydroxychloroquine 600mg dosing did not reduce PCR-confirmed SARS-CoV-2 infection [2] . Our results suggest that prophylaxis with hydroxychloroquine 400mg weekly is ineffective, and recommendations for prophylactic use, such as those for healthcare workers in India, should be reconsidered.

When justifying widespread implementation of a prophylactic intervention, it is paramount to consider and predefine a required minimum efficacy. With the Food and Drug Administration (FDA)'s suggestion that a minimum efficacy of 50% was required for a Covid-19 vaccine to be approved, we hypothesized that a 50% relative risk reduction in confirmed or probable Covid-19 would be clinically meaningful and powered the study design as such. Our estimates of incidence of Covid-19 (confirmed or symptomatic) will be valuable for future studies of chemoprophylaxis and vaccine trials.

Enrolling participants was a challenge. We enrolled 84% of all participants (1250 of 1483) in the first two weeks of the trial. During April 21-24, 2020, a series of small or retrospective studies highlighted safety concerns of hydroxychloroquine [21, 22] , which resulted in a warning from FDA regarding arrhythmias and QT prolongation [23] . Thereafter, our enrollment precipitously declined. An additional study in May, which is now retracted [24], further discouraged enrollment. Enrollment was stopped on May 26, 2020, due to futility in A c c e p t e d M a n u s c r i p t ongoing participant recruitment. Enrollment in other North American randomized clinical trials of hydroxychloroquine was also impeded (Dee Dee Wang, personal communications). As a result of premature enrollment termination and inadequate power, it is difficult to estimate the potential societal benefit, if any, in widespread implementation.

The major limitation of this trial relates to the inherent challenges with PCR testing that have been well described-both the lack of U.S. availability and moderate reported sensitivity early in illness. The false-negative rate of PCR testing has been reported to be 38% (Range 18-65%) on the first day of symptoms, gradually decreasing thereafter [25] . In our study, 39%

(38/97) had Covid-19-compatible symptoms with a negative PCR test; however, 30 of those PCR tests were performed before symptoms began, when false negatives can be expected [25] . To address this, we included healthcare workers with symptomatic Covid-19-compatible illness despite negative PCR but separately reported this group. Further supporting this decision, Covid-19-compatible symptoms warrant self-isolation from work for 14 days for healthcare providers and reporting to occupational health, per CDC guidelines, even if PCR testing is negative [26] .

However, it is unknown what proportion of persons with symptomatically compatible disease truly have SARS CoV-2 infection, which remains a shared limitation to all outpatient Covid-19 trials in the absence of a diagnostic test with improved sensitivity. Hypothetically, if reported symptoms were due to another respiratory illness, such as influenza, they should have been evenly distributed between groups due to randomization. If one compares only PCR-confirmed disease, there was no statistical difference between groups. Secondly, our trial was limited by weekly self-report of outcomes, subject to recall bias. As mentioned previously, insufficient dosing of hydroxychloroquine remains a limitation of this study. Finally, our trial was left underpowered due to impediments to participant recruitment. With the actual sample size A c c e p t e d M a n u s c r i p t accrued, more rapid initial pace of accrual (85% recruited in the first two weeks), lower lost to follow up rate in the control group, and control group event rate of 7.9%, there was 80% power with alpha of 0.05 to detect a 59% relative effect per arm and a 53% relative effect (i.e. hazard ratio of 0.47) when pooling the two hydroxychloroquine arms together. Nevertheless, the effect size estimates derived from our data will inform current policy and aid in the design of future clinical trials testing prophylaxis or vaccines.

An effective means of prophylaxis for high-risk healthcare workers remains a critical need in the context of a growing and relentless pandemic. The COVID PREP study evaluated the effectiveness of once-weekly and twice-weekly hydroxychloroquine to prevent Covid-19 in high-risk healthcare workers across the United States and Canada. There was no statistically significant reduction in the incidence of Covid-19 in our trial. However, investigation into more frequent dosing may be warranted. Prior to embarking on further clinical trials, and for current studies to complete enrollment, the perception of equipoise in the medical community and the public will need to change dramatically.

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Aerosol-generating procedures performed per week -mean (SD)

*No pregnant women enrolled, 30 women reported breastfeeding at baseline

We thank the healthcare workers around North America who volunteered to participate in this trial in order to obtain knowledge for society. We thank the thoughtful service of DSMB members: Drs. Mark Siedner, Lynn Matthews, Jeff Klausner, Bozena Morawski, and TomChiller. We thank institutional support from Drs. Jakub Tolar, Peter Igarashi, Brad Benson, and Tim Schacker.

The funders did not contribute to the design, collection, management, analysis, interpretation of data, writing of the report, nor the decision to submit the report for publication.

Dr. Boulware collaborates with multiple pharmaceutical companies making novel antifungal medicines for cryptococcal meningitis in public-private research partnerships, without any financial interests or payments from these companies.All other authors have no potential conflicts.

A c c e p t e d M a n u s c r i p t A c c e p t e d M a n u s c r i p t A c c e p t e d M a n u s c r i p t

The Lancet E. Expression of concern: Hydroxychloroquine or chloroquine with or without a macrolide for treatment of COVID-19: a multinational registry analysis. Lancet 2020; 395: e102.A c c e p t e d M a n u s c r i p t