Thread by @podehaye

"important contribution", read the article or follow the thread below... 1/n

👇

https://twitter.com/DominikMenges/status/1388522481275871233

This table is from the paper. "Ratio of persons with + test result after app notification per all SARS-CoV-2 positive cases" ranges from 0.6% to 1.8% in Zurich and 0.2% (!) to 0.6% in Switzerland as a whole, during various periods including the beginning of the 2nd wave. 2/n

Bear in mind these numbers are very likely to be overestimates.

The paper doesn't account for 3 (overlapping) effects:
- household contact w/ notification;
- non-household but already-p2p-traced contact
(see pdehaye.medium.com/lies-damn-lies… );

3/n

- already in quarantine but asymptomatic and only way to get a free test is to declare being notified (see github.com/digitalepidemi… )

4/n

So, "important contribution", w/ at best 1% of cases detected throughout CH attributable to SwissCovid?

You will be the judge.

But you should also consider the following before making a decision.

5/n

SwissCovid has costs as well.
a/ more useless quarantines than through manual CT
b/ privacy costs (on Android it currently leaks just about eveything to 3rd party apps, no official communication by @BAG_OFSP_UFSP)
c/ $ for strange TikTok ads

6/n

d/ significant burdening of cantonal staff - training, supervision, manual busy work
e/ subtle but consequential discrimination effects introduced by pre-selecting your sample through access to a digital device
github.com/digitalepidemi…

7/n

e/ opportunity cost: other efforts, such as science-based backwards contact tracing (not Bluetooth pseudo-engineering!)

You might say the last one is unfair. Well...

8/n

It's not like it wasn't predictable that SwissCovid would catch so few cases. See July 2020 tweet:

https://twitter.com/podehaye/status/1285554437352718342?s=20

9/n

It has also been known for a looong time that COVID was "overdispersed", which leads to different tracing strategies than those applicable to the flu, that need their own specific digital support tools.
nature.com/articles/d4158…
10/n

For the life of me, this is what is most puzzling in all this. @C_Althaus had a paper in January 2020 on its overdispersion. Why didn't that insight diffuse faster into the Scientific Task Force?

https://twitter.com/C_Althaus/status/1296781541650178048?s=20

11/11