What will happen to me if I take part?

As we don’t know whether Hydroxychloroquine can reduce the risk of healthcare workers contracting the coronavirus, or whether the dose of Hydroxychloroquine as a prevention treatment is important, we need to compare the treatment (Hydroxychloroquine) with Placebo in different dosing regimens.

There are 3 groups in this study and each group will receive a different treatment. You will be allocated one of the groups for this trial in a random way (by chance) using a computer algorithm. You will have a 3:3:2 chance of receiving either:

• Hydroxychloroquine daily (loading dose of 2 x 200mg twice daily for first two days (800mg/day), then dosed daily; 200mg/day) plus weekly placeboli;
• Hydroxychloroquine weekly (loading dose of 2 x 200mg twice daily for first two days (800mg/day), then dosed weekly; 400mg/week) plus daily placebo; or
• Placebo (loading dose of 2 tablets twice daily for first 2 days, then dosed daily with an additional 2 tablets weekly).

Below is a list of the assessments and procedures that we will carry out in the trial. Some assessments rely on local logistics and/or NHS resources and if not undertaken will not affect your participation in the trial. These include COVID-19 tests, respiratory screens and blood samples across visits 1-3, as outlined below:

• Visit 1: Baseline (duration, approximately 45 minutes at hospital): Where possible, we will perform a standard COVID-19 test/s (this may not be analysed until a later date due to current limitations in obtaining results) and respiratory screen for common respiratory viruses. These will be taken by nasal and throat swab, or blood, as per current clinical practice guidelines at each visit. We will ask you about your medical history, concomitant medications, and current work setting.

  You will also be invited to give a blood sample (blood group, serum and genetic store; the maximum amount of blood taken will be approximately 30ml [2 tablespoons] at each visit).

  We shall then explain how to complete some simple / brief questions to monitor your health weekly. These can be completed over web/app-based interfaces or telephone.

  Following this, you will be randomised to a treatment group and given your treatment pack containing your trial medication for the first 7 weeks.

• Visit 2: Interim> (duration, approximately 45 minutes at hospital): This will take place approximately 6 weeks after baseline Visit 1. You should not take your trial medication on the morning of this visit. Where possible, we will perform a second COVID-19 test/s and respiratory screen as before.

  We will review your current work setting, concomitant medications, and ask about any adverse events you may have experienced. You will also be invited to give another blood sample (drug levels and serum store).

• Visit 3: End of study (duration, approximately 45 minutes at hospital): This will take place once you have completed your trial medication, approximately 13 weeks after baseline visit 1.

  Where possible, we will perform a final COVID-19 test/s and respiratory screen. We will review your current work setting, concomitant medications and ask about any adverse events. You will be invited to give a final blood sample (serum store).

• Weekly assessments (duration, approximately 5-10 minutes performed remotely via telephone or web/app interface): These will be undertaken weekly for 13 weeks, 2 of which will be conducted during hospital visits 2 and 3.

  We shall ask you to confirm you have taken your medication over the preceding week, and report any new or review any ongoing adverse events. We will also ask you to complete brief questions to assess your symptoms, self-reported recovery and incidence of health care usage.