Post by PennyPost by BrritSki<https://www.spectator.co.uk/article/do-masks-stop-the-spread-of-covid-19->
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Here's the text below. Anne has referenced the original research which I
haven't read myself, but I'm happy to have it summarised for my by a
Professor of EVIDENCE-BASED medicine at Oxford.
Do face masks work? Earlier this year, the UK government decided that
masks could play a significant role in stopping Covid-19 and made masks
mandatory in a number of public places. But are these policies backed by
the scientific evidence?
Yesterday marked the publication of a long-delayed trial in Denmark
which hopes to answer that very question. The ‘Danmask-19 trial’ was
conducted in the spring with over 3,000 participants, when the public
were not being told to wear masks but other public health measures were
in place. Unlike other studies looking at masks, the Danmask study was a
randomised controlled trial – making it the highest quality scientific
evidence.
Around half of those in the trial received 50 disposable surgical face
masks, which they were told to change after eight hours of use. After
one month, the trial participants were tested using both PCR, antibody
and lateral flow tests and compared with the trial participants who did
not wear a mask.
In the end, there was no statistically significant difference between
those who wore masks and those who did not when it came to being
infected by Covid-19. 1.8 per cent of those wearing masks caught Covid,
compared to 2.1 per cent of the control group. As a result, it seems
that any effect masks have on preventing the spread of the disease in
the community is small.
Some people, of course, did not wear their masks properly. Only 46 per
cent of those wearing masks in the trial said they had completely
adhered to the rules. But even if you only look at people who wore masks
‘exactly as instructed’, this did not make any difference to the
results: 2 per cent of this group were also infected.
When it comes to masks, it appears there is still little good evidence
they prevent the spread of airborne diseases. The results of the
Danmask-19 trial mirror other reviews into influenza-like illnesses.
Nine other trials looking at the efficacy of masks (two looking at
healthcare workers and seven at community transmission) have found that
masks make little or no difference to whether you get influenza or not.
But overall, there is a troubling lack of robust evidence on face masks
and Covid-19. There have only been three community trials during the
current pandemic comparing the use of masks with various alternatives –
one in Guinea-Bissau, one in India and this latest trial in Denmark. The
low number of studies into the effect different interventions have on
the spread of Covid-19 – a subject of global importance – suggests there
is a total lack of interest from governments in pursuing evidence-based
medicine. And this starkly contrasts with the huge sums they have spent
on ‘boutique relations’ consultants advising the government.
The only trials which have shown masks to be effective at stopping
airborne diseases have been ‘observational studies’ – which observe the
people who ordinarily use masks, rather than attempting to create a
randomised control group. These trials include six studies carried out
in the Far East during the SARS CoV-1 outbreak of 2003, which showed
that masks can work, especially when they are used by healthcare workers
and patients alongside hand-washing.
But observational studies are prone to recall bias: in the heat of a
pandemic, not very many people will recall if and when they used masks
and at what distance they kept from others. The lack of random
allocation of masks can also ‘confound’ the results and might not
account for seasonal effects. A recent observational study paper had to
be withdrawn because the reported fall in infection rates over the
summer was reverted when the seasonal effect took hold and rates went
back up.
This is why large, randomised trials like this most recent Danish study
are so important if we want to understand the impact of measures like
face masks. Many people have argued that it is too difficult to wait for
randomised trials – but Danmask-19 has shown that these kind of studies
are more than feasible.
And now that we have properly rigorous scientific research we can rely
on, the evidence shows that wearing masks in the community does not
significantly reduce the rates of infection.
WRITTEN BY
Prof Carl Heneghan & Tom Jefferson
Carl Heneghan is professor of evidence-based medicine at the University
of Oxford and director of the Centre for Evidence-Based Medicine Tom
Jefferson is a senior associate tutor and honorary research fellow at
the Centre for Evidence-Based Medicine, University of Oxford