A group from Medical School University of Tokyo, etc. has reported on changes in neutralizing antibody titers from sequential blood samples collected from Jan. 2020 to Apr. 2020 in Japan.
https://www.thelancet.com/journals/eclinm/article/PIIS2589-5370(21)00014-6/fulltext
After the infection onset, it seems that the neutralization titer is maintained for a several months. In the figure below, 95% CI is shown in gray color, and the red line shows the median value. As for the pathogenicity of SARS-CoV-2 via antibody-dependent enhancement (ADE) activity, numerous studies are ongoing in the world. But, no studies describing an increase in pathogenicity due to ADE have been reported yet, so that authors are thinking that the possibility of ADE would be limited.
