Thread by @DrEricDing

📍FREE RAPID ANTIGEN TESTS FOR ALL IN AUSTRIA—*5 free rapid antigen home tests per month* starting March 1st for every person—pickup in pharmacies. Austria 🇦🇹 #COVID19 positivity has doubled from 3.1% to 6.4% in 4 days, along with worrisome #B1351 surge.🧵
derstandard.at/story/20001241…

2) there are some variation by week, but this is a noted increase says @dberghofer.

Day / tests / positive /%

Thu / 50.444 / 1.577 / 3.1
Fr / 46.981 / 1.731 / 3.7
Sa / 34.958 / 1.433 / 4.1
Sun / 24.791 / 1.184 / 4.8
Mon / 19.179 / 1.225 / 6.4

3) There are many kinds of #COVID19 testing strategies. But a population wide public health screening and weekly screening that Austria 🇦🇹 is doing, even if imperfect sensitivity, is meant to “rake” out most infectious cases, says @michaelmina_lab. So this is good move.

4) While not perfect for forming bubbles; This repeated screening strategy is effective over repeated screens sequentially... even if there is test failure once or twice, it would pick up most cases, and can pick up positives later. Figure by @michaelmina_lab & @K_G_Andersen.

5) the ones Austria government 🇦🇹 gives for free currently looks like this, I’m told. Unclear the brand, but it’s a 10 min rapid antigen.

6) Austria 🇦🇹 has one nasty outbreak of #B1351 variant in Tyrol ski region - the one that is bad for reinfection that WHO warned last week - and is semi evasive against some vaccines (but J&J & Novavax vaccines still have 50-60% efficacy against B1351).

https://twitter.com/drericding/status/1359135923615719428?s=21

7) Again, this population repeated screening is different from testing for bubble formation, which one should not do without quarantine. The lack of a quarantine & *no masks* before an attempted bubble led to this. Again, repeated population screening is VERY different!

https://twitter.com/drericding/status/1360878855922348033

8) This article articulates how there are MANY kinds of testing. Population screening for public health different than diagnostic, not surveillance like wastewater, and not for “entrance” into bubbles. Read this piece by @michaelmina_lab @K_G_Andersen. science.sciencemag.org/content/371/65…

9) I’m told Austria is also imposing a rule that to visit any hair dresser, one must first test negative within 48 hour window before visit. Not sure if that is a foolproof strategy, but given FFP2 (KN95) masks used in all shops and transit, it could be safe.

10) Here is Austria’s rapid testing protocols and parameters. PPV (Positive Predictive Value - % positives that are true) is 57% if the pre-test probability is over 5% (local positivity % is best proxy of this). If Austria is at 6% positivity, then PPV would be ~60%. Not bad.

11) Here are more simulated testing probabilities. False positives can always be PCR eliminated later. A few false negative on a repeated test is not that bad for a single test - we can likely “rake out” out more true positives on repeat screens. sozialministerium.at/dam/jcr:8a36ed…

12) We can get out of this pandemic if EVERY COUNTRY does *REPEATED* rapid test. The key is repeated tests for everyone. This will rake out as many people as quickly as possible to isolate if they test positive. Don’t use for bubbles. But do use them to end the pandemic sooner.

13) But they key is to make them either free or very cheap - like $1-3 each. Countries need to all do this. Don’t be afraid of a few false negatives - like raking leaves 🍁, if we can find the majority of positive cases each day, we can quickly stop overall onward transmission.