Medical Expert’s Advice on Wearing a Mask

A few days ago, our state representative in the 102 posted a 2015 article by Dr. C. Raina MacIntyre (et al). You can view the article at In the paper, Dr. MacIntyre and colleagues argue that medical masks are better for healthcare workers than cloth masks. Notably, the authors don’t argue for no masks. Indeed, based on my reading, I felt that the representative’s quote “My mask harms me, your mask harms you” was a misunderstanding of the article–hopefully not a deliberate one.

However, my saying so could be viewed as just more partisan politics. So I decided to ask an expert for her opinion. Below I’m including the personal correspondence I received from June 2 with Dr. MacIntyre, who our representative has already acknowledged as an expert on this topic. One thing I think is important to note: she highlights how the US–and I will add, specifically Pennsylvania–could use mask design and manufacturing to bolster our economy. Our legislators could have been working on programs to do just that, helping both our community’s health and our economy. The time is running out–if it’s not already past–for us to heed the advice of the scientists and experts in order to preserve our fragile return to a more normal lifestyle. Otherwise, we will end up with another surge of disease and be in a worse position than we have been.

And now, Dr. MacIntyre’s message.

See attached paper and my commentary in Lancet yesterday. []

We have had a huge number of inquiries about our 2015 RCT of cloth masks, with some desperate HCW in the US asking me “is it better I wear no mask when I work?”. This has horrified me to the extent that we have published a direct response to the original paper and another commentary (see below).

My position is, if a HCW cannot get proper PPE, they should not work.   I agree with Trisha Greenalgh’s commentary that countries should take responsibility and scale up production.

However, some HCW will choose to work (or be forced in some cases) in substandard PPE.  Especially as CDC is recommending bandanas. For them, I think it is important there are recommendations to help them navigate through the various home-made mask options.  There are some basic design principles which can improve the filtration and fit of a cloth mask, plus recommendations on daily washing.  Here is what we wrote in response to the barrage of communications about our 2015 trial:

I have cited some of the relevant work that can inform design of a good cloth mask.  This is a newer paper with some relevant data:

And this one I think is very interesting because they show that a nylon stocking improves the performance of all kinds of masks including cloth and surgical – probably by creating a better fit and forcing air through the face piece, I would guess.

Meanwhile we are analysing the washing data from our cloth mask study – it would seem there was an association between infection and self-washing compared to washing the masks in the hospital laundry.  We will submit this somewhere to further inform the field. It’s possible the people who reported self-washing actually didn’t wash as frequently as they reported.

On community use of masks, I do believe in universal face mask use for COVID 19, if we can provide good guidance on design. The folded Tshirt and ear-loop method demonstrated by your surgeon general is a poor design.  If the CDC is recommending bandanas, they need to be doing the research – but research to date suggests single layer masks are poor, as are untreated cotton (the Konda paper above suggests chiffon or polyester blends are best). The fabric needs high thread count, fine weave and water resistance. Most studies only test filtration and do not test water resistance.  Some of the good designs I have seen include multiple layers with cotton batting or other filter material between the layers.  I do believe, from the papers I have read that designing a good cloth mask is possible.  UFMU is important, along with distancing, because of the substantial capacity of pre and asymptomatic transmission, especially if society is being opened up again.

The US of all countries should be able to scale up production of surgical or cloth masks (and give people jobs while doing so) and it is a travesty that they have not, and that they are auctioning off the medical stockpile to private companies.