1/

Masks:

Dr. Tam today on non-medical masks:

-"wearing non-medical masks, even if you have no symptoms, is an additional measure that you can take to protect others around you in situations where physical distancing is difficult to maintain." https://twitter.com/Jeffslack660/status/1247198995581030400

2/

She goes on:

-"...wearing a non-medical mask has not been proven to protect the person wearing it."

-"Cannot back off public health measures" and continues to recommended physical distancing, hand hygiene, and cleaning high touch surfaces

3/

Recall there are 2 different (slightly overlapping) questions:

1. Does wearing a mask protect me from getting #COVID19?

And

2. If everyone wore a mask, would this help stop or slowdown the spread of the virus?

*in Jan/Feb/March we were mostly asking question 1 in Canada

4/
Re: individual protection by masks in community

https://tinyurl.com/tqo369t :

-Lots of strong opinions here and that is fine

-If you want to wear a mask, go for it

-Just be mindful that masks may not provide the level of protection that many may think - its as simple as that

5/
And for the record, I was/am skeptical about the benefits of protecting uninfected individuals by mask-wearing outside of healthcare environments...maybe this works, maybe not (see points #2&4)

BUT it is also very clear masks may help protect those around you if you are sick

6/
And question #2 is interesting - can we reduce community spread with cloth masks given critical shortage of medical masks?

Given the growing evidence of (1) pre-symptomatic and (2) sub-clinical transmission, this makes sense in theory, but there are still several questions...

7/
Some questions include:

Will we see a measurable reduction in transmission attributed to cloth masks in community settings?

What is the threshold for reducing community transmission with different levels of adherence of mask wearing? (Some will wear them, others will not).

8/
Other questions:

If people are to wear non-medical masks "in situations where physical distancing is difficult to maintain," shouldn't they be wearing them at home? And wear them all the time while at home?

These are the closest contacts at greatest risk of infection.

9/
My guess is that this could show benefit in specific settings where we are not able to practice physical distancing well - (e.g. at home, perhaps in some work environments) but may be difficult to measure.

Still, hopefully people are able spread apart in most settings.

10/
As per my previous post - I am open minded to new to data that drives public health policy.

Many are overly dismissive of masks.

And many make wide leaps and claims from data generated from individuals (e.g. mask protection) to populations.

I don't think either is fair

11/
As with any intervention where we do not have quality data, being open minded to possible outcomes is key:

These can may be POSITIVE (reduced transmission) or NEGATIVE (could this backfire for reasons we have yet to consider?)

What works in one place may not work elsewhere

11/

But contrary to what some in public health/medicine AND the pro-mask group say, we do not have solid data to guide us in this situation.

And when you hear about "the distinction between absence of evidence and evidence of absence” please consider point #11 above.