Initial studies proven a rapid decrease in IgG concentrations against both S- and N-proteins in the 1st 2?months following illness [9,13], while recent large-scale studies have shown antibody persistence for up to 4?months after analysis [6,8]. antibodies were detectable in 99.5% of participants (195/196) at 6?weeks post illness. Their GMC gradually decreased between weeks 1 (20.1 AU/mL, 95%CI: 16.9C24.0), 3 (15.2 AU/mL, 95%CI: 13.2C17.6; YF-2 p? ?0.001) and 6 (9.4 AU/mL, 95%CI: 7.7C11.4; p? ?0.001). RBD-ACE2-inhibiting antibody titres and anti-RBD antibody concentrations strongly correlated at each timepoint (all r? ?0.86, p? ?0.001). Disease severity was associated with higher initial anti-RBD and RBD-ACE2-inhibiting antibody titres, but not with their kinetics. Conclusions Neutralizing antibodies persisted at 6?weeks in almost all participants, indicating more toughness than initially YF-2 feared. Anti-RBD antibodies persisted better and even improved over time, probably related to the preferential YF-2 detection of gradually higher-affinity antibodies. (%)58 (29.0)Ethnicity, (%)?Caucasian163 (81.5)?Hispanic13 (6.5)?Mixed8 (4.0)?African6 (3.0)?Asian4 (2.0)?Others2 (1.0)?Not provided4 (2.0)(%)Median durations, days (IQR)?Acute?Myalgia147 (73.5)5 (3C8)?Headache142 (71.0)6 (3C10)?Cough126 (63.0)10 (4C17)?Fever123 (61.5)3 (2C6)?Nose discharge110 (55.0)7 (3C10)?Chills107 (53.5)3 (1C4)?Dyspnoea87 (43.5)7 (4C15)?Diarrhoea76 YF-2 (38.0)2 (1C5)?Arthralgia75 (37.5)5 (3C10)?Thoracic pain56 (28.0)6 (3C10)?Nausea50 (25.0)4 (2C6)?Dysphagia45 (22.5)5 (2C8)?Abdominal pain40 (20.0)3 (2C6)?Rash22 (11.0)6 (2C14)?Vomiting12 (6.0)2 (1C4)?Subacute?Fatigue174 (87.0)15 (8C21)?Anosmia138 (69.0)19 (10C38)?Dysgeusia133 (66.5)14 (7C30)?OthersFrequency, (%)Kgs, median (IQR)?Excess weight loss81 (40.5)3 (2C4)? em Mean viral weight /em , SD NFATC1 (log10 copies/mL)6.8??1.7 Open in a separate window SARS-CoV-2, severe acute respiratory syndrome coronavirus 2; ICU, rigorous care unit; IQR, interquartile range. aImpact on daily life was assessed using scales with ideals in the range 1C5. bSymptom denseness score is the product of the total number of acute symptoms and the total duration (days) of each sign. Anti-RBD antibody reactions At 1, 3 and 6?weeks, all participants had detectable anti-RBD antibodies (Fig.?2 A). Anti-RBD GMCs improved progressively and significantly at each of the three appointments (Fig.?2A): from 74.2 U/mL (95%CI: 62.7C87.8) at month 1 to 103.2 U/mL (95%CI: 87.9C121.2; p? ?0.001) at month 3 and 123.3 U/mL (95%CI: 103.4C147.0; p? ?0.001) at month 6. Anti-RBD antibodies improved over time among the whole cohort (Fig.?3 A). At 6?weeks, 36.7% of participants (72/196) showed anti-RBD values (U/mL) that were at least two-fold higher than at 1?month, while only 4.6% (9/196) had two-fold lower ideals, and anti-RBD antibodies remained stable (0.5C2-fold change) for 58.7% of participants (115/196) (Supplementary Material Fig.?S1A). Open in a separate windowpane Fig.?2 Evolution of (A) anti-RBD (anti-receptor binding website of viral spike protein), (B) anti-N (anti-viral nucleoprotein), and (C) surrogate disease neutralization assay (sVNT) between 1, 3 and 6?weeks following illness by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). COI, cut-off index; RT-PCR, reverse-transcription polymerase chain reaction. The bars represent the geometric mean concentration (GMC) with 95% confidence interval. The dashed lines represent the respective assays cut-offs. Open in a separate windowpane Fig.?3 Reverse cumulative distribution curves for (A) anti-RBD (anti-receptor binding website of viral spike protein), (B) anti-N (anti-viral nucleoprotein), and (C) surrogate disease neutralization assay (sVNT) at 1, 3 and 6?weeks following illness by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). COI, cut-off index; RT-PCR, reverse-transcription polymerase chain reaction. The dashed lines represent the respective assays cut-offs. Inside a latent growth model without covariates, anti-RBD concentrations improved with time (estimate?=?0.040, 95%CI: 0.030; 0.050; p? ?0.001), and their switch over time differed among individuals (estimate?=?0.003, 95%CI: 0.001; 0.005; p 0.004) (Supplementary Material Fig.?S1A). The level of anti-RBD antibodies at 1?month did not predict their kinetics in the following 5?weeks (estimate?=?C0.005, 95%CI: C0.011; 0.001; p 0.088). Anti-N antibody reactions At 1, 3 and 6?weeks, 97.5% (194/199), 99.0% (194/196) and 98.0% (192/196) of participants had detectable anti-N antibodies, respectively (Fig.?2B). Anti-N GMCs gradually increased between weeks 1 (32.6, 95%CI: 27.5C38.6) and 3 (51.1, 95%CI: 43.5C60.1) and subsequently decreased YF-2 between weeks 3 and 6 (34.0, 95%CI: 28.0C41.3) (Fig.?2B). Anti-N antibodies peaked at 3?weeks (Fig.?3B). Neutralizing.