Okay, new paper out in @TheLancetInfDis.

Yes, this guy was reinfected.

Yes, he got sicker the second time around.

No, it doesn't mean that this is common or that reinfection leads to enhanced disease. https://www.thelancet.com/journals/laninf/article/PIIS1473-3099(20)30764-7/fulltext

I wrote about reinfection back in August when there was an asymptomatic case of reinfection reported in Hong Kong. Bottom line: with only a handful of cases, we don't know what this means. https://slate.com/technology/2020/08/coronavirus-reinfection-hong-kong-study.html

A few days later, I tweeted about the preprint for this case and spoke to the great @apoorva_nyc, who has been on this beat for months about it for a brief piece. https://twitter.com/angie_rasmussen/status/1299429093495042048?s=20

When a pandemic infects millions of people worldwide, we expect to see rare events emerge. Even though our immune systems work in generally the same way, we are all different and respond to infections in our own unique and special ways.

For example, we know that even though most people develop antibodies after #SARSCoV2 infection, some don't. The patient in Hong Kong did not. There was no sample available to collect from the patient in Nevada, but if he didn't, maybe that's why he was susceptible to reinfection.

Or maybe the Nevada patient had a rare immune response that predisposed him to enhanced disease on re-exposure, either through antibody-dependent enhancement, Th2 hypersensitization, autoreactive immunity, who knows?

But we DON'T know if this is very prevalent. So far, nothing indicates that people are getting reinfected all the time, much less getting enhanced disease during their second bout with COVID-19.

A few months ago, I asked my PhD mentor, @profvrr, what he thought about anecdotal reports of reinfection, as he had interviewed a physician on his (great) podcast #TWiV about it. He wisely responded that many people seem to have forgotten their basic virology & immunology...

...He pointed out that if we were constantly getting reinfected with lethal coronaviruses and getting sicker every time, humanity would have been laid low by SARS classic or MERS-CoV. But most of us do mount effective immune responses to SARS-CoV-2 just like most other viruses.

That doesn't preclude the possibility of "long COVID" or persistent infection (not yet observed AFAIK) or reinfection (convincingly observed twice). But for most people, our immune systems are working exactly as they usually do.

We don't learn much about horses by chasing unicorns, and the same is true for studying immune responses. Reinfection is interesting and should be studied, but until we have evidence that it is common, or that it's associated with increased disease severity, stay the course.

Vaccines often produce more potent, lasting immunity than natural infection (another reason to eschew the "herd immunity" strategies besides killing millions), so if anything you should take this as a reminder for why we need a safe, effective vaccine.