Hydroxychloroquine not effective in preventing COVID-19 in people exposed to virus, new Canadian-led study finds

In-depth: New hydroxychloroquine study A new study led by the MUHC confirms that hydroxychloroquine does not prevent COVID-19

Montreal — Hydroxychloroquine - a drug traditionally used to treat arthritis and that has been touted by some, including U.S. President Donald J. Trump, as a COVID-19 drug - is not effective in preventing the disease in people exposed to the virus that causes it, according to a new Canadian study.

That was the main finding in the first double-blind, randomized, placebo-controlled clinical trial of the effectiveness of hydroxychloroquine in preventing the development of COVID-19.

The clinical trial was led by the McGill University Health Centre (MUHC) in Montreal, in collaboration with researechers from the University of Manitoba, the University of Alberta and the University of Minnesota. The results of the trial were published Wednesday in the New England Journal of Medicine.

“While we had hope this drug would work in this context, our study demonstrates that hydroxychloroquine is no better than placebo when used as post-exposure prophylaxis within four days of exposure to someone infected with the new coronavirus,” said Dr. Todd Lee of the MUHC, one of the study's lead authors.

Researchers tested 821 asymptomatic adults in the U.S., Quebec, Manitoba and Alberta who had been exposed to COVID-19, at home or in a healthcare setting. Of those test subjects, 719 said they had "high-risk exposure," meaning they had been within two metres of someone confirmed to have had COVID19 for more than 10 minutes without wearing personal protective equipment (PPE). Researchers said the subjects were by and large healthy and young, with an average age of 40.

Within four days of having been exposed to the virus, the patients were randomly given either hydroxychloroquine or a placebo, which they took for five days, with the strongest dose taken on Day 1. Researchers said independent analysts studied the anonymized results.

“This is the gold standard method for this type of intervention,” said Dr. Emily McDonald of the MUHC. “It is incredibly important that we complete randomized controlled trials so that we have the best available evidence for how to prevent the spread of COVID-19.”

The trial found that 107 of the 821 test participants developed COVID-19 - both confirmed and probable cases - during the 14 days in which they were followed after being exposed. Of those who developed COVID-19, 49 had received hydroxychloroquine, while 58 people who received the placebo developed it. (Two people, one in each group, were hospitalized; none of the participants died).

"We found that there was no statistical difference between patients who got the placebo -- which was a vitamin pill -- versus those who received the active drug hydroxychloroquine," Lee said.

Researchers also found that "side effects like nausea and abdominal discomfort were more common for patients taking hydroxychloroquine compared to placebo (40% vs. 17%), but no serious treatment-related adverse reactions were reported, including any heart arrhythmia."

‘’Our study’s results set politics aside and provide unbiased evidence to guide practice in the prevention of COVID-19 and reinforce the importance of randomized clinical trials as we work together nationally and internationally to combat the novel coronavirus,’’ said Dr. Ryan Zarychanski of the University of Manitoba.

The study concluded that "More research is needed to determine whether hydroxychloroquine can be effective for the early treatment of COVID-19, and whether pre-exposure prophylaxis could be effective in high-risk populations," noting that various trials are ongoing around the world, including in Canada.

At the McGill University Health Centre, a trial looking at early treatment in the community is underway.

"I would have loved to have a positive study, but in circumstances like this you need the negative studies too so you can redirect attention," Lee said.

- The Canadian Press contributed to this report