Source: Science Direct

Simova I, Vekov T, Krasnaliev J, Kornovski V, Bozhinov P,
Hydroxychloroquine for prophylaxis and treatment of COVID-19 in health care workers, New Microbes
and New Infections,


Hydroxychloroquine (HCQ) exerts antiviral effects through several mechanisms. Our initial experience suggests that HCQ could be used for prophylaxis of COVID-19 infection in health care workers (HCW) and could help to control the virus in the early disease stages. We suggest a prophylactic strategy with HCQ for autumn-winter-spring 2020-2021.

Providing adequate health care is vitally important during the COVID-19 pandemic to keep morbidity and mortality low. Health care workers (HCW) are key guarantees for this process, and they must feel safe and adequately protected, which includes reliable prophylactic measures (1).

Hydroxychloroquine (HCQ) could exert antiviral effects, essential for prophylaxis and early treatment of COVID-19, through several mechanisms: 1) endosomal pH increase, which inhibits SARS-CoV-2 entry through the host cells’ membranes; 2) inhibition of ACE2 cell receptor glycosylation, which impedes SARS-CoV-2-receptor binding; 3) blocking the transport of SARS-CoV-2 from early endosomes to endolysosomes, which prevents the release of viral genome; 4) immunomodulation; 5) limiting the post-viral cytokine-storm syndrome (2, 3).

We share the experience of the Bulgarian Cardiac Institute (BCI) regarding the use of HCQ for prophylaxis and treatment of COVID-19 in HCW.

BCI comprises seven hospitals and eight medical centers, with around 1200 HCW, covering more than two-thirds of Bulgarian territory.

Since March 2020, many of our employees were in close contact with COVID-19 cases. We offered prophylaxis with HCQ 200 mg qd for 14 days to 204 of them. 76.4% of the group (156 HCW) used HCQ and neither of them presented with COVID-19 symptoms. Unfortunately, out of the rest 48 HCW that refused HCQ prophylaxis, three developed symptoms and tested positive for COVID-19.

During the last seven months, 38 HCW at BCI tested positive for COVID-19, half of them symptomatic.

We suggested the following treatment regimen as an early home-based therapy for them: azithromycin 500 mg qd; HCQ 200 mg tid and Zn up to 50 mg qd for 14 days. 33 (86.8%) of them undertook this treatment, with symptoms abolishing between 2nd and 4th day, none of them requiring hospitalization and with a negative PCR on 14th day for all.

The rest five HCW (13.2%) employed alternative treatment regimens, none of them including HCQ. Three of them still tested positive at 14th day and two of them required hospitalization.

All HCW (191) treated with HCQ, took Zn as well. We performed ECGs at baseline, on 3rd and 5th day of HCQ-treatment with QTc measurement. Baseline QTc was 412 ± 23 ms, 3rd day QTc: 429 ± 27 ms, and 5th day QTc: 427 ± 31 ms, p>0.05 for all comparisons. We registered QTc increase ≥60 ms in five HCW. QTc increased >470 ms in one male and >480 ms in three female HCW. In all these occasions HCQ was stopped. We did not register any rhythm disorders.

A possible drawback of HCQ prophylaxis is the risk for selecting resistant microorganisms, as has been described for Plasmodium spp. However, at present we do not have any data about SARS-CoV-2 resistance to HCQ (4).

In conclusion, our experience at BCI suggests that HCQ could possibly provide protection against infection with SARS-CoV-2 (prophylaxis), and could, if used early, help control the COVID-19 infection (treatment).

Based on this experience, we at BCI adopted a new prophylactic strategy for HCW starting from the 2nd half of October 2020. This includes alternative months of HCQ intake (200 mg qd) and months without therapy. We are planning to continue this prophylaxis regimen throughout the autumn, winter, and spring months.

Central figure: Use of HCQ for prophylaxis and early treatment of COVID-19 (upper panel) and
proposed prophylactic scheme for autumn-winter-spring 2020-2021

  1. Tadesse DB, Gebrewahd GT, Gebre GT, Knowledge, attitude, practice and psychological
    response toward COVID-19 among nurses during the COVID-19 outbreak in Northern
    Ethiopia, 2020, New Microbes and New Infections, `
  2. Prodromos C, Rumschlag T, Hydroxychloroquine is effective, and consistently so used
    early, for Covid-19: A systematic review, New Microbes and New Infections,
  3. Roussel Y, Raoult D, Hydroxychloroquine recommendations toward the world: first
    evaluations, New Microbes and New Infections,
  4. Boggild A, Brophy J, Charlebois P, Crockett M, Geduld J, Ghesquiere W, et al. Summary
    of recommendations for the prevention of malaria by the Committee to Advise on
    Tropical Medicine and Travel (CATMAT). Can Commun Dis Rep. 2014; 40(7):118-132.
    doi: 10.14745/ccdr.v40i07a01

Related: Hydroxychloroquine as pre-exposure prophylaxis against COVID-19 in health-care workers: A single-center experience

HCQ is effective for COVID-19 when used early: analysis of 132 studies

How hydroxychloroquine works at the cellular level

Open Letter from Medical Doctors and Health Professionals to All Belgian Authorities and All Belgian Media

India: Post Exposure Prophylaxis with Hydroxychloroquine (HCQ) for the Prevention of COVID-19, a Myth or a Reality? The PEP-CQ Study

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