Best rundown of the Canadian covid app I have seen so far. A couple of comments re privacy, equity and effectiveness. https://twitter.com/mgeist/status/1289998824304386048

Privacy. Installing the app has the same privacy implications as just having wifi or Bluetooth turned on and not having the app installed. People can’t learn anything about you from the app’s random identifiers that they can’t learn from your wifi or Bluetooth MAC address.

Unless you walk around with Bluetooth and wifi turned off, there is no privacy penalty when installing the app.

This changes slightly if you test positive and choose to share your random identifiers. In theory, and with a lot of foresight and effort, someone could have installed a tracker beacon, caught you in it, managed to tie your identity to the identifiers and deduce you had Covid.

This requires an enormous amount of effort resulting in a fairly small information gain (that you had Covid) which very likely could have been gotten through other means much easier. On the upside, uploading your random identifiers can help stop transmission chains.

I’d rate the privacy risk as very low and will happily upload my random identifiers in the event I test positive, knowing that this will protect people down the transmission chain.

There are equity concerns around the app only being l accessible to people with smartphones, and only those with compatible OS. That’s part of the reason why an app like this is only one of many tools on the fight.

And it’s another reason why everyone that can install the app should install it. The app doesn’t protect users from getting Covid-19, it helps protect them from spreading it by alerting people early of possible exposure so that they can self-isolate and stop the chain.

The app does not protect users, it protects their potential contacts. Which still leaves people in economically disadvantages communities more vulnerable, but not using the app if you could only worsens that.

Which brings us to the last point, effectiveness. Studies have shown that, when used in conjunction with traditional contact tracing as we are doing in Canada, these kind of apps start to become helpful when about 16% of the population has it installed.

And usefulness increases as more people install it. A much-cited University you Oxford preprint suggest that at 60% adoption rate the app could keep Covid in check even in the absence of other strong interventions. https://github.com/BDI-pathogens/covid-19_instant_tracing/blob/master/Centralised%20and%20decentralised%20systems%20for%20contact%20tracing.pdf

In other words, the more people install it (and share their random identifiers if they test positive), the more effective the app becomes. So please consider installing it. (And of course we also need provinces other than Ontario to get on board too.)