Is there evidence for COVID-19 reinfection?

[blimix]

There's some well earned worry about COVID-19 reinfection, amid anecdotal reports from doctors that people who had mild or asymptomatic cases before are now getting reinfected, and having it worse the second time. We need to do a quick thought experiment here.

Imagine two universes. In universe 1, people with mild or asymptomatic cases of COVID-19 can get reinfected. In universe 2, they cannot.

Let's look at universe 2 (no reinfection). Lots of people who catch a cold, or who have been exposed but not infected, get tested. COVID-19 tests have a false positive rate: Up to 30%, for some of them. These false positives are (mis)identified as infected, with mild or no symptoms. Later, some of these folks catch COVID-19 for real.

In universe 2, doctors share stories of their patients who got COVID-19 twice (but only severely the second time), because of the initial false positives. In universe 1, doctors share stories of their patients who got COVID-19 twice, because it's happening (and also because of false positives).

At this point, both universes look the same! The fact that we are hearing these anecdotes is not evidence that people can get reinfected. We would be hearing them either way.

...

(I'm not saying people can't get reinfected, either. I'm saying that panicking with the newfound knowledge that they *can* is premature. We will know more later, if and when reliable testing methods start to be used for mild and asymptomatic cases.)

Comments

[eirias]

The epi people I follow on Twitter also think it’s possible some of these are the “long form” infections that never cleared, despite perhaps a negative test in the middle of the series.

[blimix]

Thanks! Yeah, I thought about false negatives when I read the first doctor's report, and forgot by the time I hastily wrote this post.