The is from Michael Osterholm's Group at the University of Minnesota.  "A new study from China showed that antibodies faded quickly in both asymptomatic and symptomatic COVID-19 patients during convalescence, raising questions about whether the illness leads to any lasting immunity to the virus afterward.”

This raises a question of whether there may be a lasting immunity and that includes herd immunity.

https://www.cidrap.umn.edu/news-perspective/2020/06/chinese-study-antibodies-covid-19-patients-fade-quickly