Thread by @twpiggott

The first @CochraneCanada CAN-PCC Prevention Guideline recommendation is out:
*We suggest masking for asymptomatic adults in community settings be used for the prevention of COVID-19 infection to prevent COVID-19 condition.* (Cond Rec, Low Cert Evidence)

Here's what we found. No surprise, masks work. Their effectiveness at prevention of COVID-19 infection and therefore Post COVID Condition increase at higher risks of transmission. With 100 people infected per 1000, masks could prevent *17 cases per 1,000*.

An additional *12 cases per 1,000* could be prevented with use of a respirator style masks vs medical/surgical mask.

The panel judged the undesirable effects (harms) of mask use as trivial.

The panel judged that mask use would probably increase health equity.

The panel, in what is innovative in @GRADE_WG guidelines, also considered planetary health impacts of different kinds of masks.

We also modelled that if all Canadians (population 41 million) used a reuseable elastomeric mask instead of disposable respirator for 120 days of mask use per year significant reductions in CO2e (produced from @NRC_CNRC Greenhouse Gas Equiv Calc): ? oee.nrcan.gc.ca/corporate/stat…

There's a lot of nuance and rich information to unpack in this work by a wonderful panel, but masks work to prevent COVID-19.

You can learn more about the guidelines and the many recommendations yet to come here:

canpcc.ca

Direct link to the recommendation on masks is here:
can-pcc.recmap.org/recommendation…

Recs on masking in LTC, out-of-hospital clinical settings, and pediatrics will be coming soon. Other prevention recs on interventions for primary and secondary prevention being worked on urgently by the panel.
Lots more great work to from this project & the other guideline panels

You may have questions about this as a conditional recommendation.
In @GRADE_WG
-Strong Rec: virtually all people should follow;
-Conditional Rec: may be more individual/nuanced based on individual values & preferences;
You can learn more here