Covid-19 Gambles

[echoes]

I posted this earlier https://www.pnas.org/content/118/4/e2014564118. Am I misinterpreting the conclusions? Genuine question.

I've still not read all of it yet, and I do want to do it justice - that may take some time. Unless I'm also misreading the conclusions, they are not very, er.., conclusive. But I'll be back to it.

I don't disagree that there are very plausible theories as to why masks may help, it's just that the relevant and quality RCTs don't appear to support them.

 

[JohnW2]

I don't disagree that there are very plausible theories as to why masks may help, it's just that the relevant and quality RCTs don't appear to support them.

As I've said, on the basis of what I've seen, I thing that the jury is still out, and I would be more inclined to modify your statement to say that they are have been few (if any) RCTs that have been adequate to detect small benefits of mask wearing, if they exist.

I don't think any of us are expecting that masks produce 'large' benefits. If 'we' were to be remotely consistent in our attitude to risk, then a tiny tiny benefit (which would require ginormous trials to detect) would be enough to warrant a recommendation to wear masks - if 'we' (not me ) are concerned about a risk of "a few per million" of death as a side effect of a vaccine, then, to be consistent, we should also be concerned about a risk of "a few per million" of death due to not wearing a mask - i.e. if wearing masks resulted in avoidance of death in just "a few per million" mask-wearers, then consistency would suggest that we should advocate the wearing of masks.

However, one has to admit that "consistency" has not be a conspicuous feature of 'our' decision-making during this crisis.

As for me, so long as I believe that 'the jury remains out', I remain personally inclined to err on the side of caution.

It sounds as if Boris is later today going to go a fair way to adopting my view, but (in my opinion) in a ridiculous 'sitting on the fence' ('passing the buck') fashion - by telling people that they "may" now stop wearing masks and practising 'social distancing') but, at least in some environments "should not" stop wearing them, or stop practising 'social distancing'. Of course, by passing the buck in this way, it means that, if things go pear-shaped, the government will be able to blame 'the choice of the people', rather than themselves!

It still seems to me, that this whole business could 'back-fire' (i.e. be counter-productive). I am increasingly hearing people on TV, and amongst my friends/family/contacts, saying that IF significant numbers of people start going into shops, trains, pubs, restaurants, theatres or whatever without wearing masks (and without 'social distancing'), then they will stop going to such places - so it could end up as a very poor way of 'opening up the economy'!

Kind Regards, John

 

[echoes]

As I've said, on the basis of what I've seen, I thing that the jury is still out, and I would be more inclined to modify your statement to say that they are have been few (if any) RCTs that have been adequate to detect small benefits of mask wearing, if they exist.

The jury may be out for forever. The only RCT than I am aware of that was of sufficient quality (the Danish 'Danmask' study) found no benefit. That is entirely consistent with there being no benefit.

I don't think any of us are expecting that masks produce 'large' benefits. If 'we' were to be remotely consistent in our attitude to risk, then a tiny tiny benefit (which would require ginormous trials to detect) would be enough to warrant a recommendation to wear masks - if 'we' (not me ) are concerned about a risk of "a few per million" of death as a side effect of a vaccine, then, to be consistent, we should also be concerned about a risk of "a few per million" of death due to not wearing a mask - i.e. if wearing masks resulted in avoidance of death in just "a few per million" mask-wearers, then consistency would suggest that we should advocate the wearing of masks.

If we were remotely consistent in our attitude to risk and advocated mask wearing for a pretty much immeasurable benefit then we wouldn't have a bath, ride a bicycle, drive a car, cross a road or go swimming.

However, one has to admit that "consistency" has not be a conspicuous feature of 'our' decision-making during this crisis.

Oh absolutely! In fact I'd go further and say that from a public health prospective decision making has been arbitrary. From a behavioural psychology perspective it's been very calculated. This should alarm you.

It sounds as if Boris is later today going to go a fair way to adopting my view, but (in my opinion) in a ridiculous 'sitting on the fence' ('passing the buck') fashion - by telling people that they "may" now stop wearing masks and practising 'social distancing') but, at least in some environments "should not" stop wearing them, or stop practising 'social distancing'. Of course, by passing the buck in this way, it means that, if things go pear-shaped, the government will be able to blame 'the choice of the people', rather than themselves!

He's triangulating. The man is now stuck in a squalid mess of his and his policy advisers' making. He's managed to frighten a good proportion of the population to the point of hypochondria & agoraphobia rather than admit that there is very little governments can do to control the spread of a respiratory virus among the largely healthy and mobile population. And I agree that when (not if), there is resurgence of flu or Covid-19 or whatever viral disease is circulating this autumn and winter (as there is most years), he'll be blaming the public.

It still seems to me, that this whole business could 'back-fire' (i.e. be counter-productive). I am increasingly hearing people on TV, and amongst my friends/family/contacts, saying that IF significant numbers of people start going into shops, trains, pubs, restaurants, theatres or whatever without wearing masks (and without 'social distancing'), then they will stop going to such places - so it could end up as a very poor way of 'opening up the economy'!

That says much about how people have been terrified by a carefully executed propaganda campaign and how such a campaign has been driven by TV and the media. Still, that's where we are. It's a right old mess!

 

[denso13]

The only RCT than I am aware of that was of sufficient quality (the Danish 'Danmask' study) found no benefit.

There are differing views on that, for example, https://blogs.bmj.com/bmj/2020/11/2...-actually-show-that-masks-protect-the-wearer/

"The results of DANMASK-19 do not argue against the benefit of masks to those wearing them but actually support their protective effect."

 

[bernardgreen]

admit that there is very little governments can do to control the spread of a respiratory virus among the largely healthy and mobile population.

That is a fact...

Remove the mobility of the population and you will significantly reduce the spread.

 

[plugwash]

The question is whether that is a cure worse than the disease...................

A year is more than 1% of a lifetime.

 

[EFLImpudence]

Great posts Echoes.

 

[echoes]

That is a fact...

Remove the mobility of the population and you will significantly reduce the spread.

Myopic. You would have to reduce the mobility to the point where the society no longer functioned, basically placing the vast majority under house arrest indefinitely. That would kill far more people than a virus with a mean infection fatality rate of 0.15% (albeit much more dangerous for the immune-compromised). And then what happens afterwards? Does the virus magically disappear?
You also need to look at where the virus did actually spread most and do the most damage before suggesting quarantining the healthy: dominated by hospitals and care homes - indoor settings where susceptible folk abound.

 

[JohnD]

Remove the mobility of the population and you will significantly reduce the spread.

how's that working out for Australia?

 

[JohnW2]

The jury may be out for forever. The only RCT than I am aware of that was of sufficient quality (the Danish 'Danmask' study) found no benefit. That is entirely consistent with there being no benefit.

Hmmmm. Have you actually read the paper (see here) ? In particular, have you read the conclusion (my emboldening) ...

Conclusion: The recommendation to wear surgical masks to supplement other public health measures did not reduce the SARS-CoV-2 infection rate among wearers by more than 50% in a community with modest infection rates, some degree of social distancing, and uncommon general mask use. The data were compatible with lesser degrees of self-protection.

As I recently said, I don't think that any of us would have seriously expected an effect anything as great as a 50% reduction in infections, although much lesser degrees of that could be a useful addition to the cocktail of control measures - and, as you can seen, the authors conceded that the results were compatible with 'lesser' effects (less than 50% reduction in infections).... and if we look at the actual results ...

... Infection with SARS-CoV2 occurred in 42 participants recommended masks (1.8%) and 53 control participants (2.1%). The between-group difference was -0.3 percentage point (95% CI, -1.2 to 0.4 percentage point; P= 0.38) (odds ratio, 0.82 [CI, 0.54 to 1.23]; P= 0.33). ....

The 0.3% difference is potentially misleading because of the very low infection rates in both groups, and actually means that there were about 14% less infections in the mask group than the control group (and that's probably well into the ballpark of degrees of benefit that I would consider 'worthwhile').

However, with such low infection rates (1.8% and 2.1%), the trial was pitifully statistically underpowered (far too small) to detect, as 'statistically significant', a difference between 1.8% and 2.1%. The sample size required to have a 90% power to detect as 'significant' (p<0.05) a difference between 1.8% and 2.1% would be about 102,000 (about 51,000 per group), so it's hardly surprising that the difference failed to reach statistical significance with this study's 6,024 subjects (3,030 + 2994) - so I would question your description of this study as being "of sufficient quality". It might well have been well designed and conducted, but it was far far too small to detect, with any confidence, differences between such small infection rates.

If the study had been considerably larger, and the infection rates in the two groups still 2.1% and 1%, then that 14% less infections with masks would have become 'statistically significant', and even you may have conceded that a 14% reduction was 'worthwhile' as a component of the package of 'control measures'.

If that is the 'best' study available (and I personally know of none better), then that strongly reinforces my view that the jury is very much out.

Kind Regards, John

 

[mikeey84]

The subtle distinction in the Danmask study is that it found no benefit to "encouraging people to wear masks".

It did not say there was no benefit to wearing a mask.

An RCT to ultimately say whether masks are effective would be very difficult, as wearing them, or not, would have a substantial change on people's behaviour.

 

[denso13]

The study itself states;

"Although no statistically significant difference in SARS-CoV-2 incidence was observed, the 95% CIs are compatible with a possible 46% reduction to 23% increase in infection among mask wearers. These findings do offer evidence about the degree of protection mask wearers can anticipate in a setting where others are not wearing masks and where other public health measures, including social distancing, are in effect. The findings, however, should not be used to conclude that a recommendation for everyone to wear masks in the community would not be effective in reducing SARS-CoV-2 infections, because the trial did not test the role of masks in source control of SARS-CoV-2 infection."

 

[echoes]

There are differing views on that, for example, https://blogs.bmj.com/bmj/2020/11/2...-actually-show-that-masks-protect-the-wearer/

"The results of DANMASK-19 do not argue against the benefit of masks to those wearing them but actually support their protective effect."

I've read that. It's quite a leap from the study itself, which states:

'Infection with SARS-CoV-2 occurred in 42 participants recommended masks (1.8%) and 53 control participants (2.1%)'.
'...the difference observed was not statistically significant'.
'3030 participants were randomly assigned to the recommendation to wear masks, and 2994 were assigned to control; 4862 completed the study.'

The author extrapolates the 18% apparent reduction in infections (and himself acknowledges the dangers in doing so) based on 11 data out of 4862.

Again, we are the realm of "probably", "could" and "maybe". This is no basis for legally enforced mandates.

 

[JP_]

.

 

[denso13]

Again, we are the realm of "probably", "could" and "maybe".

Well perhaps, but the study you are relying on as demonstrating there is no benefit says there is maybe a 46% reduction to maybe a 23% increase in infection among mask wearers using their 95% CIs. I'd say that's hardly conclusive of "no benefit".