New mask guidelines, and update on the Swiss Cheese model, and a newsletter hiatus
Let’s get started with a bit of housekeeping. This is going to be my last newsletter for the next 2-3 months, as I’m going on paternity leave.
I’ll come back in a few months, hopefully to a world with much more positive news to write about.
But let’s cover a couple of quick topics before hiatus.
First, what to make of the new CDC guidance on masks
The CDC just updated mask guidelines based on COVID risk in your individual community.
According to the new guidelines, only those who live in counties of high COVID risk should be wearing masks indoors in public:
COVID risk in each county is based not just on infection risk but also how the hospital system is holding up - the goal is focused on preventing hospitals from getting overrun and along with preventing severe disease.
You can make the same critique of the current guidance that you could make about past mask wearing guidance: it’s capricious and arbitrary.
Our original pandemic sin is that we never conducted the clinical trials necessary to answer important questions on non-pharmacologic interventions; as a consequence, we still live in a world where we don’t know just how effective mask wearing is in slowing COVID spread.
But in the age of readily available vaccines and tons of “natural” immunity, the best way to think mask wearing is that its function is much more to protect the individual wearing the mask than it is about protecting the community.
If you’re high risk for getting severe COVID (and by high risk, the predominant variables are things like history of organ transplant, immune system compromise, active cancer), you’re probably better off continuing to wear an N95 or KN95 mask when you’re inside in a crowded situation.
And if you’re just concerned about getting sick - or you’re unvaccinated or unboosted - it probably makes sense to keep wearing a mask.
Bringing the temperature down on the masking discussion is a good thing for all of us. If you want to wear a mask, you should have access to a free high quality mask like an N95 or KN95.
Second, why the Swiss Cheese model of risk assessment isn’t all that great
I wrote a previous newsletter on the concept of the Swiss Cheese model of COVID prevention. This graphic basically summarizes that newsletter:
The point is that in a pandemic, there are number of imperfect solutions that all may stop viral spread a little bit. When you add up quite a few imperfect solutions in series, you end up with a pretty impressive impact on pandemic trajectory.
While I strongly advocated this model at the time, I’ve come to think that it’s a bit too simplistic to the point of being misleading.
The biggest issue with the Swiss Cheese model is that it implies that all the slices of cheese have the same impact. But all interventions are not created equal - there are big differences in how important each one is.
Vaccines are so much important when it comes to pandemic spread than avoiding touching your face. The Swiss Cheese model gives a false sense of equality among interventions.
In the pre-vaccine age, I think the story from this model was much more truthful. In a world where anyone who wants a vaccine can get one, I’m less persuaded that it’s a useful way to graphically illustrate what’s going on.
We’re often fooled by graphics that look great. Add this one to the list of cognitive biases to be aware of: visualization bias.
So that’s it for now - see you all in a few months
Please continue to send me more questions, comments, and any topics you’d like to see covered.
Will look forward to writing more newsletters and interacting with all of you more in the coming months.