It seems at least some people are NOT immune from reinfection
https://apple.news/AEa2W19goTKyeMnZr1BMbdA
That is relapse, not reinfection, though your link has a good discussion of all sorts of hypothetical explanations, none of which there is actual evidence of given we don't have any widely used antibody tests yet. From your link:
Lei Xuezhong, the deputy director of the infectious diseases center at the West China Hospital, told People’s Daily that hospitals were testing nose and throat samples when deciding whether patients should be discharged, but new tests were finding the virus in the lower respiratory tract.
Despite this also from your link, there's nothing to base this on given the available tests.
Allen Cheng, professor of infectious diseases epidemiology at Monash University in Melbourne, said it wasn’t clear whether the patients were re-infected or had remained “persistently positive” after their symptoms disappeared. But he said the details of the Japan case suggested the patient had been reinfected.
And this is true with dengue virus but there's no evidence people are getting a more serious second bout of disease:
Other experts have also raised the possibility of “antibody-dependent enhancement”, which means exposure to viruses might make patients more at risk of further infections and worse symptoms.
It has implications though that persons deemed well might still be shedding virus and be contagious.
I looked into this:
I found one report (still from a news report) that a Dr Li QinGyuan was seeing the return of positive tests in people previously cleared. There was no mention of relapsing disease.
https://www.usatoday.com/story/news...00-deaths-can-you-get-virus-again/4804905002/
Li QinGyuan, director of pneumonia prevention and treatment at China Japan Friendship Hospital in Beijing, said a protective antibody is generated in those who are infected.
"However, in certain individuals, the antibody cannot last that long," Li said. "For many patients who have been cured, there is a likelihood of relapse."
Li urged patients who have recovered from COVID-19 to be vigilant in their hygiene, such as washing their hands often.
In another report which I cannot read all of:
https://www.caixinglobal.com/2020-0...uangdong-tested-positive-again-101520415.html
14% of Recovered Covid-19 Patients in Guangdong Tested Positive Again
This version in Chinese that can be translated is an accessible version.
http://china.caixin.com/2020-02-28/101521885.html
Antibody production isn't likely to be being tested given how new that testing is:
https://www.sciencemag.org/news/202...se-antibody-test-track-coronavirus-infections
Singapore claims first use of antibody test to track coronavirus infections
https://www.cdc.gov/coronavirus/2019-ncov/about/testing.html
Serology Test for COVID-19
CDC is working to develop a new laboratory test to assist with efforts to determine how much of the U.S. population has been exposed to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the virus that causes COVID-19.
The serology test will look for the presence of antibodies, which are specific proteins made in response to infections. Antibodies can be found in the blood and in other tissues of those who are tested after infection. The antibodies detected by this test indicate that a person had an immune response to SARS-CoV-2, whether symptoms developed from infection or the infection was asymptomatic. Antibody test results are important in detecting infections with few or no symptoms.
Initial work to develop a serology test for SARS-CoV-2 is underway at CDC.
What it appears is that they are using the PCR antigen testing that looks for the virus, not the antibodies. Those tests are using multiple serum samples from blood to saliva to feces. Without knowing how they determined the virus was clear and how it was found again we don't really know what is going on here.
Lancet has recently reported on research on serial testing of viral loads to track what happens with infected people.
https://www.thelancet.com/journals/...0)30113-4/fulltext?dgcid=raven_jbs_etoc_email
Sample sizes are small. Virus was found as much as 15 days after it was first detected. If you look at the graph for patient #2 their viral load went up and down before it cleared.
I don't think any of this suggests failed immune response, rather it looks more like people continue to test positive for virus after recovery. This is not unusual. For some viral pathogens it's common that they remain contagious after the symptoms resolve.
It's going to take more time before this is sorted out.