WHO joins Merck, Europe against generic anti-parasite drug ivermectin for Covid-19

"This applies to patients with COVID-19 of any disease severity," Janet Diaz, a top WHO official for clinical care response, told reporters of the WHO recommendation, saying it was "based on very low certainty of evidence" that ivermectin helps.

The WHO's review was based on a survey of 16 trials of ivermectin involving 2,400 people, including those comparing it with hydroxychloroquine, an older malaria medicine that has been discredited as a COVID-19 treatment. There were very few placebo-controlled studies of ivermectin.

"We certainly need more data in order to make informed decisions," said Bram Rochwerg, an associate professor at Canada's McMaster University and a co-chair of the WHO panel that reviewed ivermectin.

He said the data available was sparse and likely based on chance, though he said "high quality, trustworthy trials" were still merited.

"We did see an increase in adverse effects in patients that were randomised to ivermectin," he said, citing gastrointestinal upsets and headaches.

Worldwide, he said, there are 66 trials of ivermectin registered, with 60,000 participants, so more data on its impact on the pandemic could be coming.

"We are fighting this overuse of unproven therapies - especially some of these repurposed drugs - in various parts of world without evidence of efficacy," Diaz said. "There can be more harm than any good."