Hydroxychloroquine fails as postexposure prophylaxis for COVID-19

Researchers have found that giving hydroxychloroquine as postexposure prophylaxis for COVID-19 did not prevent illness.

The study, published in the New England Journal of Medicine, enrolled adults who had exposure to someone with confirmed COVID-19 at a distance of less than 6 ft for more than 10 minutes while wearing neither a face mask nor an eye shield (high-risk exposure) or while wearing a face mask but no eye shield (moderate-risk exposure).

Within four days of exposure, participants were randomly assigned to receive either placebo or hydroxychloroquine (800mg once, followed by 600mg in six to eight hours, then 600mg daily for four additional days).

The incidence of new illness compatible with COVID-19 was not significantly different between those receiving hydroxychloroquine (11.8%) and those receiving placebo (14.3%). Also, the researchers noted that side effects were more common with hydroxychloroquine (40.1% versus 16.8% for placebo), but that no serious reactions were observed.

However, Boulware et al. did note that their trial had limitations, because the vast majority of participants were unable to access testing in the US, so it was difficult to determine how many actually had COVID-19.

'Whether preexposure prophylaxis would be effective in high-risk populations is a separate question, with trials ongoing,' they also stressed.