Researchers analysed the contents of the video sharing platform’s most widely viewed clips as of March 21.
The Google-owned service has taken action to prevent the spread of misinformation around Covid-19, as have other tech giants.
In a study of 69 videos which have collectively accumulated more than 257 million views, 19 (27.5%) were found to feature non-factual details – totalling over 62 million views.
The reliability and quality of the content of each one was assessed using scoring systems.
Professional and government agency videos scored significantly higher for accuracy, usability, and quality across all measures than any of the other sources, but did not feature prominently among viewing figures.
A paper published in the BMJ Global Health journal said that while good quality accurate information put out by government bodies and experts is widely available on YouTube, it is often hard to understand and lacks popular appeal, so does not have the reach it needs.
Among the 19 misleading videos, around a third originated from entertainment news, with network and internet news sources each accounting for around a quarter. Consumer videos made up 13% of the total.
“This is particularly alarming, when considering the immense viewership of these videos,” write researchers Heidi Oi-Yee Li, Adrian Bailey, David Huynh and James Chan.
“Evidently, while the power of social media lies in the sheer volume and diversity of information being generated and spread, it has significant potential for harm.
“The education and engagement of the public is paramount in the management of this pandemic by ensuring public understanding of, and therefore adherence with, public health measures.”
A YouTube spokeswoman responded, saying that any content that disputes the existence or transmission of Covid-19, as described by the WHO and local health authorities, is in violation of YouTube policies.
For borderline content that could misinform users in harmful ways, it reduces recommendations.
She said: “We’re committed to providing timely and helpful information at this critical time, including raising authoritative content, reducing the spread of harmful misinformation and showing information panels, using NHS and WHO data, to help combat misinformation.
“We have clear policies that prohibit videos promoting medically unsubstantiated methods to prevent the coronavirus in place of seeking medical treatment, and we quickly remove videos violating these policies when flagged to us.”