So the WHO has been recommending 3 layer masks since June, but Health Canada has been recommending 2 layer minimum.
Today Dr Tam announced that Health Canada now recommends the same mask configuration as the WHO. Now to me, this isn't a huge deal. Health Canada is a strong body with a lot of expertise and I trust their judgement. If their opinion changes over time, that makes sense. We learn and adapt, its how the scientific method works.
However, its language like this:
When pressed about the sudden change for Canada, Tam said the research has evolved.
That pisses me off. Any step change is sudden! Its not like Tam could have annouced last week that Health Canada recommends 2.5 layer masks, or that they are thinking that maybe 2 layers isn't maybe good enough.
No you wait till there is evidence and then recommend.
Its like asking an electron why its NOW decided to move to another quantum level. There is no inbetween and any change will be sudden.
A better question, which may have lead to a nuanced answer, would have been, "Was there a single study that changed the balance to 3layer minmums?" Or "can you elaborate on what factors in the studies that you used to make you judgement?".
Both of those questions get to the PROCESS of the decision making, that process is what's important and what we should be judging, not the outcomes.
Source: https://www.cbc.ca/news/politics/three-layer-mask-tam-1.5787946