"The study, which focused on 37 asymptomatic and 37 symptomatic patients, showed that more than 90% of both groups showed steep declines in levels of SARS-COV-2–specific immunoglobulin G (IgG) antibodies within 2 to 3 months after onset of infection, according to a report published yesterday in Nature Medicine. Further, 40% of the asymptomatic group tested negative for IgG antibodies 8 weeks after they were released from isolation."
Second, an additional chinese study found that:
"The authors conclude in their paper that the remaining 10 percent of infected patients with no detectable antibodies, combined with the lack of antibodies in healthcare workers, suggest that “after SARS-CoV-2 infection, people are unlikely to produce long-lasting protective antibodies against this virus.”"
Third, an NIH study found that only 1% of people in their pool had "potent" antibodies. Most people in their pool had some antibodies, but often of low count or quality. This infers that either they have potent antibodies when truly sick, or just thereafter, and they quickly fade OR that they never create potent ones. Either way, that means trouble for long term herd immunity.