Persistent while declined neutralizing antibody responses in the convalescents of COVID-19 across clinical spectrum during the 16 months follow up

ABSTRACT

Elucidation the kinetics of neutralizing antibody response in the coronavirus disease 2019 (COVID-19) convalescents is crucial for the future control of the COVID-19 pandemic and vaccination strategies. Here we tested 411 sequential plasma samples collected up to 480 days post symptoms onset (d.a.o) from 214 convalescents of COVID-19 across clinical spectrum without re-exposure history after recovery and vaccination of SARS-CoV-2, using authentic SARS-CoV-2 microneutralization (MN) assays. COVID-19 convalescents free of re-exposure and vaccination could maintain relatively stable anti-RBD IgG and MN titers during 400[~]480 d.a.o after the peak at around 120 d.a.o and the subsequent decrease. Undetectable neutralizing activity started to occur in mild and asymptomatic infections during 330 to 480 d.a.o with an overall rate of 14.29% and up to 50% for the asymptomatic infections. Significant decline in MN titers was found in 91.67% COVID-19 convalescents with [≥] 50% decrease in MN titers when comparing the available peak and current MN titers ([≥] 300 d.a.o). Antibody-dependent immunity could also provide protection against most of circulating variants after one year, while significantly decreased neutralizing activities against the Beta, Delta and Lambda variants were found in most of individuals. In summary, our results indicated that neutralizing antibody responses could last at least 480 days in most COVID-19 convalescents despite of the obvious decline of neutralizing activity, while the up to 50% undetectable neutralizing activity in the asymptomatic infections is of great concern.