Unherd's Freddie Sayers interviewed Copenhagen University's Professor Henning Bundgaard about his randomized control trial study into the protective effects of face masks, which Sayers said "caused the predictable furor when it was published last week. Comparing a sample of 3,000 people who were wearing masks and 3,000 people who were not, 42 of the mask-wearers became infected with COVID-19 and 53 of the non-mask-wearers: a small, non-statistically-significant difference."

Sayers continued: "The self-appointed Defenders of Science were quick to move into attack mode. Oxford’s Trish Greenhalgh said it was not necessarily 'high quality science' and made some technical objections to the study; science-activists like Vincent Rajkumar, Editor-in-Chief of the Blood Cancer Journal, announced: 'Ignore the Danish study. Masks work. Wear a mask… Speaking as someone who has led 10 RCTs and knows when to ignore one'; a former CDC director lambasted the study in the same journal that published it.

"To make it worse, there were rumors that the study had been squashed or censored, rejected by medical journals on political grounds.

"But in a sign of how rash this debate has become, none of the critics seems to have taken the time to talk to the study’s authors. We spoke to the lead investigator, Professor Henning Bundgaard of the University of Copenhagen, and found him to be the most inoffensive, on-message, pro-mask advocate you could find. It turns out that the scientist they were attacking was one of their own. His view, it turns out, is that:

"Even though the protective effect is small, masks should be worn diligently wherever recommended.

"The main benefit of masks is the ‘source control’ effect, where other people are protected from you, which the study does not cover.

"The usefulness of the result is that it shows that you cannot be complacent even if wearing a mask — it must be seen as one tool among many, including social distancing, hand hygiene etc. There was no conspiracy to censor his results: even though the study was rejected from the New England Journal of Medicine, JAMA and the Lancet, he does not believe it was for political reasons, more likely simply that it was a neutral conclusion.

"He fully stands by his results and maintains that the study was carried out as scientifically as it is possible to do."

Professor Henning Bundgaard said: "I think the message should be that wearing a mask, in the correct way of course, would to some extent — not a large extent but some extent — protect you. But it’s your contribution to protect others, that we should take care of each other. All of us would hate the idea that I had a dangerous disease now I passed it on to you because I was not wearing a mask. So we have good reasons to recommend masks, I guess."

Bundgaard stated that according to the study, "it would take 300 people wearing a mask for a month to protect one person from getting an infection."