Thread by @MarcelHarmon1

Our new office policy we're finalizing essentially takes this viewpoint. In 3 of our offices, we've assessed high vaxx rates combined w/ addressing the Delta far field risk via ventilation/filtration is adequate enough for vaxxed employees (almost 100%) to go sans masks. 1/

https://twitter.com/j_g_allen/status/1446785476350861320

Even in metro areas currently deemed by the CDC as having high or substantial community transmission.

To have vaxxed employees go sans masks in our other 2 offices, relative to their current lower office vaxx rates, the Delta far field risk needs to be addressed through... 2/

some combination of additional ventilation/filtration improvements, increasing vaxx rates, setting lower occupancy limits, or having non-vaxxed employees WFH - we are still assessing the best path forward for each of those locations.

We estimated the far field risk for... 3/

each office location using our Facility Infection Risk Estimator (branchpattern.com/research/facil…), taking office vaxx rates into account & assuming 1 infected individual is present. We also assessed our eACH for each office.

For the near field risk, we are able to locate seats a... 4/

minimum of 3' apart (greater in many cases). Though we recognize depending on airflow patterns 3' isn't necessarily adequate in some cases. We will be asking vaxxed employees to mask up in situations where they have to be in close proximity (< 3') to others for more than a... 5/

brief encounter, such as during a meeting. For the 3' - 6'ish range, it will likely be up to employees to decide if they want to wear a mask.

Once our metro rates fall w/in the moderate community transmission range, we will likely drop the near field masking requirement. 6/

But as @j_g_allen points out, this near field masking requirement may be over conservative relative to the actual risk that an infected employee, who is also shedding a lot of virus, is in the office on any given day, & that another vaxxed employee then becomes infected. 7/

As a thought exercise, I'll take the KC metro area where one of our offices resides. Let's assume actual community transmission falls somewhere between cases/100,000 & % positivity rate (though likely much closer to the former). Using CDC tracking data from 10/4, I'll... 8/

arbitrarily assign a weighting of 0.825 to the cases/100,000 & 0.175 to the % positivity rate. I'll use the resulting weighted average as an estimate of the community transmission rate and determine this for 8 counties in the metro area. I'll then average those 8 values,... 9/

weighted by each county's population. This gives me a value of 1.59% as the KC metro area's estimated average transmission rate on 10/4. The KC office has 30 employees, so if everyone is there, the probability that 1 employee is infected is 38.2% using this 1.59% estimate... 10/

of community transmission.

BUT this assumes our employees are a representative sample of the KC metro area population. They aren't, because we're almost 100% vaxxed compared to the roughly 45% - 65% fully vaccinated rates, depending on the county. 11/

In addition, our employees generally aren't in situations that potentially expose them to infected individuals as much as some other demographic groups in the metro area. And just because an infected person is present doesn't mean they are at their most infectious stage. 12/

These & other factors mean that the 38.2% over-estimates the likelihood of an highly infectious employee being present in the office on any given day. Maybe it's under 15%. Maybe even under 5%. And that's w/ community transmission deemed by the CDC as High. 13/

So our near field risk masking measures may be conservative, but I think even if the risk is just 5%, we'll continue w/ them until community rates drop lower. Certainly at 15% we would want to keep them. We don't want to be a link in a chain of community transmission. 14/

However, I generally feel confident going sans masks otherwise in these 3 offices that have addressed the far field risks via ventilation/filtration & vaccinations.

But it's important to note that we are able to go sans mask in our work environment, w/ current community... 15/

transmission rates what they are, because of privilege. 16/