We bought some tasteful face-masks the other day. Iād been wearing a crappy snood thing when I went into shops for a week or two, but it was a single layer of nylon and probably almost entirely ineffective.
The turnaround on mask policy has caught attention ā the UK government began by telling people they didnāt work, then ‘advising people to consider‘ using them in enclosed spaces, now mandating them on public transport; other national governments and the WHO have been on similar journeys.
To understand what happened there, itās worth reading this post. It quotes an old BMJ paper, a joke one issued at Christmas, which pointed out that there are no randomised controlled trials showing that parachutes save lives when you jump out of a plane.
Itās pretty obvious why that is; you canāt ethically make 50 people jump out of a plane with a placebo parachute. So you have to make do with observational evidence ā people who jump out of planes without parachutes tend to die more ā even though that canāt, strictly, prove causality.
The same happened with masks. You canāt have a bunch of healthcare workers walking around hospitals with no masks on, because it would put patients at risk. So the studies never got done, so the evidence remained really bad. And medical regulatory bodies demand really high standards of evidence to say something works, so if something has bad evidence, they say it doesnāt work.
Normally thatās a good thing ā it means they donāt end up licensing a bunch of crappy quack medicines ā but in this case, it led to people confidently saying āmasks donāt helpā when they meant āwe canāt prove masks help, but thereās a decent chance that they doā.
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