Characteristics of individuals included in the study.

Characteristics of individuals included in the study.</p

In-house ELISA validation.

The sensitivity and specificity of the in-house ELISAs for IgG (A) and for IgA (B) Abs against S and RBD were estimated with 40 pre-pandemic sera (Healthy C.) and 40 PCR+ COVID-19 sera. For IgG anti-S and anti-RBD Abs the cut-off point was 150 AU/well (dashed line). For IgA Abs the cut-off point for anti-S was 120 AU/well and for anti-RBD 80 AU/well (dashed lines).</p

IgA anti-S and anti-RBD levels post-vaccination.

Anti-S (blue) and anti-RBD (red) Abs were measured on Day0, 21, 42, 90, 180 and 270 (n = 56). Cut-off values for anti-S and anti-RBD Abs were 120 AU/well and 80 AU/well, respectively (dashed lines). Asterisks (***) indicate statistically significant differences (p-value < 0.001) between the compared groups. Each dot represents an individual, and error bars represent the mean value and standard deviation of the distribution.</p

IgG and IgA rate of change up to 9-months post-vaccination.

IgG (A) and IgA (B) RC values express the average change per day and were estimated for two subsequent time points: Day0-Day21 = RC0–1, Day21-Day42 = RC1–2, Day42-Day90 = RC2–3, Day90-Day180 = RC3–6, Day180-Day270 = RC6–9. Positive values indicate an increase in production, negative values imply a decrease, and values close to zero show no change in anti-S (blue) and anti-RBD (red) antibody binding. Asterisks (*) indicate statistically significant differences (p-value: *<0.05, ***<0.001). Each dot represents an individual, and error bars represent the mean value and standard deviation of the distribution.</p

Chronic or other diseases of individuals included in the study.

Chronic or other diseases of individuals included in the study.</p

Antibody levels for 34 HCWs who received a third dose of the BNT162b2 mRNA vaccine.

IgG (A) and IgA (B) anti-S (blue) and anti-RBD (red) Abs were measured on Day0, 42, 90, 270 days after the first dose on Day0 and on Day21γ, 21 days after the third dose. Asterisks (***) indicate statistically significant differences (p-value: <0.001). Each dot represents an individual and error bars represent the mean value and standard deviation of the distribution.</p

IgG anti-S and anti-RBD kinetics in a 9-month period: PCR+ individuals (red, n = 12 COVID-19), naïve individuals (green, n = 131) and suspected COVID-19 asymptomatic individuals (blue, n = 3).

IgG anti-S (A) and anti-RBD (B) Abs were measured on Day0, 21, 42, 90, 180 and 270 days after the first dose. For each group, mean and standard deviation values are given for every time-point. Asterisks (*) indicate statistically significant differences (p-value: *<0.05, **<0.001, ***0.001) between the groups of PCR+ and naïve individuals.</p

Slope comparison for anti-S and anti-RBD IgG antibodies from Day42 up to Day270.

(TIF)</p

Multivariate regression analysis results for other factors affecting the immune response to vaccination.

(PDF)</p

IgG anti-S and anti-RBD levels post-vaccination.

Anti-S (blue) and anti-RBD (red) Abs were measured on Day 0, 21, 42, 90, 180 and 270 days after the first dose on Day0. Cut-off values for anti-S and anti-RBD Abs were 150 AU/well (dashed line). Dark colored dots represent post-vaccination infected individual’s anti-S and anti-RBD IgG levels respectively. Asterisks (***) indicate statistically significant differences (p-value<0.001) between the compared groups. Each dot represents an individual, and error bars represent the mean value and standard deviation of the distribution.</p