Thread by @Kit_Yates_Maths

After hearing some underwhelming testimony last month at the #COVIDInquiry on the use of respirators, @trishgreenhalgh and I decided to write a rapid response to the @bmj_latest to set the record straight.
Here's what we wrote...
1/15
bmj.com/content/386/bm…

"Respirators outperform surgical masks; fit-testing is desirable but not essential"

Professor Susan Hopkins (UK Covid Inquiry, 18th September 2024) claimed that evidence for the superiority of respirators (which are made to an industry standard and designed to fit ...
2/15

closely around the face) over medical facemasks (which are not generally made to any quality standard and often fit loosely, leaving gaps around the sides) is “weak”.
She also claimed that respirators are of little use if they are not fit-tested.
3/15
bmj.com/content/386/bm…

Separately (26th September 2024), Sir Chris Whitty claimed (in the context of a question about protecting healthcare workers) that “just having [PPE] kit but no training often produces little or no benefit”.
4/15
covid19.public-inquiry.uk/wp-content/upl…

In @trishgreenhalgh's recent state of the science review, she and her co-authors summarised an evidence base on masks and respirators for the prevention of respiratory infections. That evidence draws on multiple study designs across different disciplines.
pubmed.ncbi.nlm.nih.gov/38775460/

That evidence is contested chiefly because some infection prevention and control scholars reject or misinterpret evidence from outside their own discipline.
6/15

Several findings from our review, which included a new meta-analysis of randomised controlled trials, challenge official statements on this topic...
7/15

1. Because respiratory pathogens transmit via the air, a face covering that seals the face closely is likely to be more effective than one that allows air to bypass the filtration material.
8/15

2. Numerous laboratory studies have shown that FFP2 and FFP3 (or their US equivalents N95 and N99) respirators, which are made to an industry standard, filter out well over 95% and 99% of infectious particles respectively.
9/15

3. Both trials [4,5] and observational studies [6] have shown that respirators provide significantly more protection to healthcare workers than medical or cloth masks...
10/15
pubmed.ncbi.nlm.nih.gov/21477136/

...so long as they are worn continuously (as opposed to being donned only for so-called ‘aerosol-generating procedures’ in patients known to be, or suspected of being, infectious).
11/15
elifesciences.org/articles/71131

4. Respirators that are not fit-tested are still significantly more effective than ordinary masks; they are as effective as fit-tested respirators in most but not all people.
12/15
pubmed.ncbi.nlm.nih.gov/20853203/

As Baroness Hallett pointed out, to claim equivalence between an industry-standard product designed to take account of the known mechanism of transmission and a non-standard product which does not defies common sense.
13/15

It also appears to reflect a lack of familiarity with key research on the topic. We are concerned that the science of masks and respirators appears to have been misunderstood, and misinformation unwittingly perpetuated, by some of the very highest-level government advisors.

An effective UK response to any future pandemic depends on a deeper engagement with this science.
\ENDS

I wrote along similar lines in my latest substack:
"Is the Covid Inquiry about learning lessons or covering backs?"
Last month's testimony on masks and airborne spread has left many bemused
substack.com/home/post/p-15…

BMJ seem to have changed the link so you can find the response here now: bmj.com/content/386/bm…