Yesterday, we reported on some new research that has just been published in the the Lancet, a journal of non-peer-reviewed research that is nonetheless viewed as an extremely credible resource. The report, published by scientists at a university in Shanghai, claimed that some COVID-19 patients showed few, or, even more alarming, no COVID-19 antibodies in their blood after recovering from the illness.

And now, another report highlighting the extremely concerning susceptibility that humans have to this virus has been released. Researchers in Seoul have found several cases wherein patients who've recovered from COVID-19 have seen the disease "reactivate", possibly because the virus was still lying dormant inside them, and had been reawakened, somehow.

The Straits Times reported that about 51 patients who had been "cured" in South Korea have tested positive again, the Korean Centers for Disease Control said during a media briefing. Rather than being infected again, the virus may have been reactivated in these people, given they tested positive again shortly after being released from quarantine, and likely didn't have time to reacquire the virus and see it go active, said Mr Jeong Eun-kyeong, the KCDC's director-general.

"While we are putting more weight on reactivation as the possible cause, we are conducting a comprehensive study on this," Mr Jeong said. "There have been many cases when a patient during treatment will test negative one day and positive another." A patient is deemed fully recovered when two tests conducted with a 24-hour interval show negative results.

Despite having one of the earliest outbreaks, South Korea has only recorded 200 deaths and reported falling new daily numbers since cases peaked at 1,189 on Feb. 29. The KCDC reported just 39 new cases on Thursday for a total of 10,423. One of the world's most expansive testing programs and a tech-driven approach to tracing infections has helped the country contain its epidemic without lockdowns or shuttering businesses.

Fear of re-infection in recovered patients is also growing in China, following a string of reports claiming some patients had tested positive again - or even died from the disease - after supposedly recovering and leaving hospital.

As of now, scientists are still trying to understand this phenomenon, and nothing is set in stone.

But we fact that there's a growing body of evidence to suggest that many people just can't build up an immunity to this drug doesn't bode well for prospects of a universally effective vaccine.