The way I understand how our immune system works is this:
During a viral infection, the patient’s body develops antibodies that are very specific to the virus that infected them – and after they’ve recovered, these antibodies don’t disappear. They go into hibernation, and are ready to wake up as soon as the same pathogen tries to contaminate the body again. This characteristic of the immune system is the same against all known viruses.
In those reported cases of “re-infections”, the people concerned had been tested in the days after their discharge from hospital, which excludes the possibility that ineffective antibodies created the impression that they had contracted the coronavirus for a second time.
I question the reliability of the Chinese tests seeing how horrendously bad their test kits are.
See here:
Spanish health officials have recommended that physicians stop all use of rapid response coronavirus test kits after a batch bought from China failed to identify contagious people.
The Spanish Society of Infectious Diseases and Clinical Microbiology issued the recommendation after it was revealed that test kits from the Chinese firm Bioeasy presented a sensitivity of 30%, meaning that only 30% of those who have COVID-19 tested positive for it. Most tests, including rapid influenza tests in the United States, require a minimum sensitivity of 80%.
See also here:
Up to 80 percent of the 300,000 rapid coronavirus test kits ordered that the Czech Republic ordered from China are not working properly, according to regional hygienists who have tried the tests.
The test kits, worth 54 million korunas (€1.83 million), show false positive as well as negative results. This is because rapid tests cannot reliably detect infection in its initial phase.
And also here:
https://news.abs-cbn.com/news/03/28/20/some-test-kits-sent-from-china-only-40-percent-accurate-doh
MANILA - The Department of Health said Saturday some COVID-19 test kits sent by China were only “40 percent accurate” based on standards of the World Health Organization.
“The first test kits sent to us by China, that showed only 40 percent accuracy, we did not use because the accuracy rate is low. That’s why we only stored them.” DOH Undersecretary Maria Rosario Vergeire said in a press briefing.
Actually antibodies do disappear after a while. It’s the ‘Memory B cells’ that retain memory of the virus (viral antigen, that is ). B cells are antibody factories. If these B cells encounter the same pathogen again, they will very quickly get into gear and start pumping out antibodies and the immune response will be much quicker.
Somebody should quickly make an effort to figure out False Positive, False Negative, alpha, beta, specificity, and sensitivity.