12-month SARS-CoV-2 antibody persistency in a Tyrolean COVID-19 cohort

Background Short-term antibody response to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been shown previously. The further development remains to be determined. Methods We prospectively followed 29 coronavirus disease 2019 cases, mean age 44 +/- 13.2 years. Except for one participant in whom rheumatoid arthritis existed, all other cases were previously healthy. We determined anti-viral binding antibodies at 2-10 weeks, 3 months, 6 months, and 12 months after disease onset as well as neutralizing antibodies (NAb) against wild type at 6 and 12 months and the B.1.1.7 and B.1.351 variants at month 12. Three binding antibody assays were used, targeting the nucleocapsid protein (NCP), the S1 subunit of the spike protein, and the receptor binding domain (RBD). Results Antibodies to the RBD persisted for 12 months in all cases with increasing concentrations, whereas antibodies to S1 dropped below cut-off point in 7 participants and NCP antibodies were above cut-off point in only 5 subjects at month 12. The NAb against wild type were detected in all but 2 samples at 12 months of follow-up but clearly less frequently when targeting the variants. In 5 participants who were vaccinated against COVID-19 there was a strong increase of antibodies against S1 and RBD as well as an increase of NAb titres against wild type and the variants. Conclusion There was a persisting antibody response against SARS-CoV-2 up to 12 months after COVID-19 with declining concentrations except for RBD and a strong increase of all antibody concentrations after vaccination.