Top scientists have warned there is a ‘troubling lack of evidence’ that face masks prevent Covid-19 infection, after a major study in Denmark found they don’t protect people who wear them.
Some governments around the world have made it mandatory to wear a face covering in public spaces, despite a lack of rigorous trials into their effectiveness.
The rationale has been that masks must be better than nothing because they block at least some virus being exhaled or inhaled by the wearer.
But a randomised study published by scientists at Copenhagen University, thought to be the best of its kind so far, found no statistical evidence that they offer any protection whatsoever.
Reacting to the finding in a column in The Spectator, Oxford University’s Professor Carl Heneghan and Dr Tom Jefferson said there had been ‘a troubling lack of robust evidence on face masks and Covid-19’.
There have only been three ‘real life’ studies comparing mask-wearers to non-mask-wearers — one in Guinea-Bissau, one in India and the new Denmark study. All have shown masks to have no benefit in preventing the disease.
But the experts added: ‘Now we have properly rigorous scientific research we can rely on, the evidence shows wearing masks in the community does not significantly reduce the rates of infection.’
The Copenhagen experts recruited 6,000 volunteers in the spring — before masks were mandatory there — and split the them into two groups, with half wearing masks in public and half not.
After a month, the mask-wearing volunteers were tested for current and previous Covid-19 infection and compared with the control group who didn’t wear them.
Results showed that, after one month, 1.8 per cent of the people wearing masks had been infected with the virus.
By comparison, 2.1 per cent of the people in the unmasked group had tested positive for Covid-19. The difference between the two groups was not found to be statistically significant.
‘The study does not confirm the expected halving of the risk of infection for people wearing face masks,’ the authors wrote in a press release.
‘The results could indicate a more moderate degree of protection of 15 to 20 [percent], however, the study could not rule out that face masks do not provide any protection.’
The team, from Copenhagen University Hospital, said the findings should not be used to argue against their widespread use, however, because masks may prevent people infecting others.
The results from the Danish study – called Danmask-19 – mirror the findings of studies into influenza.
Nine other trials looking at the efficacy of masks on influenza have found that masks make little or no difference in whether people catch the virus.
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