Abstract
In a SARS-CoV-2 seroprevalence study conducted with 1,655 working adults in spring of 2020, 12 of the subjects presented with positive neutralization test (NT) titers (>1:10). They were here followed up for 1 year to assess their Ab persistence. We report that 7/12 individuals (58%) had NT_50 titers ≥1:50 and S1-specific IgG ≥50 BAU/ml 1 year after mild COVID-19 infection. S1-specific IgG were retained until a year when these levels were at least >60 BAU/ml at 3 months post-infection. For both the initial fast and subsequent slow decline phase of Abs, we observed a significant correlation between NT_50 titers and S1-specific IgG and thus propose S1-IgG of 60 BAU/ml 3 months post-infection as a potential threshold to predict neutralizing Ab persistence for 1 year. NT_50 titers and S1-specific IgG also correlated with circulating S1-specific memory B-cells. SARS-CoV-2-specific Ab levels after primary mRNA vaccination in healthy controls were higher (Geometric Mean Concentration [GMC] 3158 BAU/ml [CI 2592 to 3848]) than after mild COVID-19 infection (GMC 82 BAU/ml [CI 48 to 139]), but showed a stronger fold-decline within 5–6 months (0.20–fold, to GMC 619 BAU/ml [CI 479 to 801] vs. 0.56–fold, to GMC 46 BAU/ml [CI 26 to 82]). Of particular interest, the decline of both infection- and vaccine-induced Abs correlated with body mass index. Our data contribute to describe decline and persistence of SARS-CoV-2-specific Abs after infection and vaccination, yet the relevance of the maintained Ab levels for protection against infection and/or disease depends on the so far undefined correlate of protection.
Highlights
We recently reported in a longitudinal seroprevalence study conducted in a cohort of working adults (n = 1,655) that SARS-CoV-2 RBD-specific antibodies (Abs) persist for at least 6 months independent of symptom severity; we further observed that COVID-19 symptoms anosmia and/or dysgeusia correlated most closely with the detection of virus-neutralizing Abs [1]
Most reports on persistence of SARS-CoV-2-specific immune parameters show that neutralization test (NT) titers and S1-specific IgG levels remain rather stable between 6 and 12 months after infection while NCP-specific Abs decline quickly [11,12,13,14,15]
SARS-CoV2-specific Ab persistence has so far not been investigated with regard to the decline kinetics of NT_50 titers and S1-specific IgG nor has a potential threshold been considered
Summary
We recently reported in a longitudinal seroprevalence study conducted in a cohort of working adults (n = 1,655) that SARS-CoV-2 RBD-specific antibodies (Abs) persist for at least 6 months independent of symptom severity; we further observed that COVID-19 symptoms anosmia and/or dysgeusia correlated most closely with the detection of virus-neutralizing Abs [1]. In order to assess SARS-CoV-2 seroprevalence in the investigated cohort at the end of the third pandemic wave in Austria and to determine Ab persistence over 1 year, the study subjects were invited to a follow up blood draw between mid-April and mid May 2021. Of the 1,655 subjects recruited in April 2020 only 12 presented with neutralization test (NT) titers >1:10 and were followed up for the kinetic and long-term persistence of Abs and memory B cells for 1 year.
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