> This study was not specifically designed to determine the duration of protection afforded by natural infection, but for the previously infected subjects the median duration since prior infection was 143 days (IQR 76 – 179 days), and no one had SARS-CoV-2 infection over the following five months, suggesting that SARS-CoV-2 infection may provide protection against reinfection for 10 months or longer.
You don’t actually know that for sure though. The following paper found PCR positives months after being infected, with a slowly decreasing odds ratio, which is in their words consistent with shedding: https://jamanetwork.com/journals/jamainternalmedicine/fullar...
Unless someone gets a PCR positive, has the virus sequenced, and then gets a separate positive later, has the virus sequenced again and can confirm they were actually infected again with live virus (perhaps using live viral culture) they can’t really be sure.
> This study was not specifically designed to determine the duration of protection afforded by natural infection, but for the previously infected subjects the median duration since prior infection was 143 days (IQR 76 – 179 days), and no one had SARS-CoV-2 infection over the following five months, suggesting that SARS-CoV-2 infection may provide protection against reinfection for 10 months or longer.