Researchers say that antibodies in patients who have become infected by the virus may decline, or even disappear, within months, suggesting immunity from an eventual vaccine could fade as well over. Only 17% of the 60% of patients who had had a particularly strong antibody response when they were fighting the virus still had those antibodies at the same levels three months later. In some cases, the antibodies disappeared entirely, the researchers found. The study, if backed up by further evidence, would further undermine the concept of herd immunity.
Link to study: https://www.medrxiv.org/content/10.1101/2020.07.09.20148429v1