Hydroxychloroquine Can’t Prevent COVID-19, Study Finds

Hydroxychloroquine is not effective at preventing COVID-19 in those with the highest risk of exposure.

In a clinical trial from the Perelman School of Medicine at the University of Pennsylvania, researchers found no difference in infection rates of hospital workers who took daily doses of hydroxychloroquine versus those who took a placebo. The results were published online in JAMA Internal Medicine on Wednesday. 

“This work represents the first randomized trial of hydroxychloroquine’s prophylactic (preventative) effect for those not yet exposed to COVID-19,” study lead author Benjamin Abella, MD, MPhil, a professor of Emergency Medicine and the director of Penn Medicine’s Center for Resuscitation Science, said in a news release. “And while hydroxychloroquine is an effective drug for the treatment of diseases like lupus and malaria, we saw no differences that would lead us to recommend prescribing it as a preventive medication for COVID-19 in front line workers.”

Hydroxychloroquine has been a matter of controversy since the early days of the pandemic, when it was introduced as a possible treatment for COVID-19. While the Food and Drug Administration (FDA) granted emergency use authorization for both hydroxychloroquine and chloroquine products in March, it revoked the authorization by June, citing ineffectiveness and a risk of serious cardiac events. 

Even though the FDA deemed the drug unfit for COVID-19 treatment, its potential role in prevention was less clear. The UPenn study is the first to offer evidence that there’s no statistically significant benefit to taking hydroxychloroquine to reduce COVID-19 risk.

Out of 125 physicians, nurses, certified nursing assistants, emergency technicians, and respiratory therapists evaluated in the study—all of whom had direct contact with COVID-19 patients—half took 600 milligrams (mg) of hydroxychloroquine every day for eight weeks, while the other half took a placebo. Neither the participants nor the researchers knew who was taking the drug versus the placebo. 

By the end of the study, 6.3% of the hospital employees taking hydroxychloroquine had contracted COVID-19, compared to 6.6% of the employees taking a placebo. This indicates the drug has no clinical benefit for prevention of COVID-19. 

Employees were tested for COVID-19 at the beginning, middle, and end of the study, and given electrocardiograms (ECGs) to screen for any heart problems associated with hydroxychloroquine. Researchers detected no difference in heart rhythms among each group, suggesting that while hydroxychloroquine was not an effective prevention method, it was also not harmful. 

The study did have its drawbacks. It was terminated early before reaching the intended 200 participants because researchers decided more participation wouldn’t influence results. In addition, 125 people is a relatively small sample size, and most of the study participants were young and healthy. The participants who contracted COVID-19 were either asymptomatic or experienced only mild symptoms. 

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