Thread by @doctimcook

Strong article @By_CJewett on AEROSOLS, COUGH, the complex discussion around risk for HEALTHCARE WORKERS and FFP3/N95 masks

With @drjulesbrown me and others

Here's a bit of the evidence behind it
1/19

theguardian.com/us-news/2021/m…

First the archetypal metanalysis by Tran which seemingly underpins the early approach by many public health organisations

Evidence base...
"We identified 5 case-control and 5 retrospective cohort studies which evaluated transmission of SARS to HCWs"
2/19

ncbi.nlm.nih.gov/pmc/articles/P…

As I often quote the excellent paper from @mugecevik shows important differences in viral dynamics between SARS and SARS-CoV-2

Infectivity from SARS-CoV-2 starts and finishes earlier
Hugely important for infection control strategies
3/19

thelancet.com/journals/lanmi…

Here is the @CDCgov webpage on modes of COVID-19 transmission

It states "COVID-19 can sometimes be spread by airborne transmission"
....but does not offer whether this is frequent or rare.
4/19

cdc.gov/coronavirus/20…

@WHO also recognise aerosol transmission

"Aerosol transmission can occur in specific settings, particularly in indoor, crowded and inadequately ventilated spaces..."
5/19

who.int/news-room/q-a-…

PHE "Airborne transmission can occur in health settings in which...treatments...generate aerosols are performed... also occur in poorly ventilated indoor spaces particularly if individuals are in the same room together for an extended period of time"
6/19

gov.uk/government/pub…

So the public health organisations acknowledge aerosol spread can occur in some settings: we need to get away from the idea they don't

But they differ in recommendation on mask use

CDC N95 where possible
WHO Surgical masks except for AGPs
PHE as WHO
7/19

Links here

CDC N95 where possible
cdc.gov/coronavirus/20…
WHO Surgical masks except for AGPs apps.who.int/iris/handle/10…
PHE Surgical masks except for AGPs
assets.publishing.service.gov.uk/government/upl…
8/19

Early in the pandemic it became clear UK social and healthcare workers were dying from COVID-19

Frontline staff mostly in non-senior roles

A disproportionate number of whom were from non-white ethnic groups and first generation migrants to UK
9/19

hsj.co.uk/exclusive-deat…

This pattern of disproportionate impact on social and healthcare workers from non-white ethnic groups and first generation migrants to UK persisted
10/19

hsj.co.uk/workforce/at-l…

Even early on it was apparent that Anaesthetists had a lower mortality than many other staff groups.
11/19

…-publications.onlinelibrary.wiley.com/doi/full/10.11…

Many hospital infection epidemiology studies followed

These showed infection 3-4 x more common in frontline staff (only) & especially
-juniors (nurses and docs)
-nurses
-healthcare assistants
-domestics

But sparing of Anaesthesia & Intensive care settings
12/19

The data on HCW infection and mortality from COVID-19 was summarised in an editorial with @DrSimonLennane

This confirmed low risk not only of infection but also of mortality for those working in ICU/anaesthesia
13/19

…-publications.onlinelibrary.wiley.com/doi/full/10.11…

Presumptions around ICU/anaesthesia risk are based on procedures designated 'aerosol generating' - ref Tran

That is now strongly challenged by groups such as #AERATOR @BristolUni & others
While emphasising importance of COUGH in aerosol generation
14/19

…-publications.onlinelibrary.wiley.com/doi/10.1111/an…

And further analysis of deaths of healthcare workers highlights certain groups are at particular risk

While this article focuses on vaccine priority the same argument and priority applies to staff protection
15/19

hsj.co.uk/coronavirus/nu…

Ambulance and transport staff stood out as high risk for infection and mortality in our analysis
16/19

https://twitter.com/doctimcook/status/1363035511397502978?s=20

A longer (more rounded) version of this argument
- both for early HCW vaccination (protection)
- and for subgroups is here @DrSimonLennane
17/19

github.com/DrSimonLennane…

This adds to an uncomfortable situation: ICU/anaesthesia most protected & also one of the lowest risk groups

The question: is low risk due to protection or circumstance?

A precautionary principle supports FFP3 (N95) masks being used more widely
18/19

rcpjournals.org/content/clinme…

But its not simple
Its non aerosols vs droplets
Its not ICU vs the rest
Its not FFP everywhere vs nowhere

There is nuance

The answers come from research & discussion not tribal posturing.

19/19