Correlation between Anti-SARS-CoV-2 Total Antibodies and Spike Trimeric IgG after BNT162b2 Booster Immunization

Abstract

Objective: In this work we monitored both total and IgG anti-SARS-CoV-2 antibodies responses after BNT162b2 vaccine booster immunization in a cohort of ostensibly healthy healthcare workers. Methods: The study population consisted of 266 subjects (median age, 46 years and interquartile range (IQR), 35–52 years; 168 females) undergoing homologous 30-µg BNT162b2 booster administration. Serum samples were collected immediately before the booster dose and 1 month after. Results: The concentration of anti-SARS-CoV-2 RBD total antibodies and anti-SARS-CoV-2 spike trimeric IgG increased by 31 (IQR, 16–53) and 22 (IQR, 11–43) folds, respectively, after receiving the BNT162b2 vaccine booster. A highly significant Spearman′s correlation was found between the relative increase (i.e., ratio of post-booster and pre-booster serum values) of anti-SARS-CoV-2 RBD total antibodies and anti-SARS-CoV-2 spike trimeric IgG (r = 0.86; p < 0.001). Conclusion: These results suggest that monitoring of post-BNT162b2 booster immunization for purposes of identifying “low responders” could be conducted almost interchangeably with either total or IgG anti-SARS-CoV-2 antibodies.

A performance comparison of two (electro) chemiluminescence immunoassays for detection and quantitation of serum anti‐spike antibodies according to SARS‐CoV‐2 vaccination and infections status

“…Nevertheless, these correlated to a lesser extent for sera from Unvac‐Ex ( ρ = 0.66) than those from Vac‐Ex ( ρ = 0.88) and Vac‐N ( ρ = 0.80), likely due to differences in the antigenic specificity of antibodies generated following vaccination or natural infection. In agreement with our findings, previous studies reported correlation levels between the Roche and DiaSorin immunoassays ranging from 0.80 to 0.93 in panels mostly comprising sera from vaccinated/naïve individuals 13–18 . The sizable difference between correlation levels across Vac‐Ex and Unvac‐Ex observed in our study are also congruent with findings by Lukaszuk et al 17 A relatively novel observation of this study relates to the impact of antibody concentration on the magnitude of quantitative discordances across the two immunoassays; in effect, for sera with <1000 BAU/ml, the DiaSorin assay returned higher values than the Roche assay, whereas the reverse was documented for sera ≥1000 BAU/ml.…”

“…In agreement with our findings, previous studies reported correlation levels between the Roche and DiaSorin immunoassays ranging from 0.80 to 0.93 in panels mostly comprising sera from vaccinated/naïve individuals. 13 , 14 , 15 , 16 , 17 , 18 The sizable difference between correlation levels across Vac‐Ex and Unvac‐Ex observed in our study are also congruent with findings by Lukaszuk et al 17 A relatively novel observation of this study relates to the impact of antibody concentration on the magnitude of quantitative discordances across the two immunoassays; in effect, for sera with <1000 BAU/ml, the DiaSorin assay returned higher values than the Roche assay, whereas the reverse was documented for sera ≥1000 BAU/ml. Although not explicitly stated, the occurrence of such differences in quantitative estimations of antibody levels provided by the Roche and DiaSorin immunoassays can be inferred from data from previous studies.…”

“…7 , 8 Numerous immunoassays permitting quantitative assessment of SARS‐CoV‐2‐S binding antibodies have been marketed, with potential differences in the analytical design, performance characteristics, immunoglobulin class measured, and the nature of SARS‐CoV‐2 antigen to which target antibodies are directed (i.e., receptor binding domain [RBD]—the S protein in its trimeric conformation, or the S1 or S2 subunits). 9 As a result, immunoassays may return discordant qualitative or quantitative results, 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 the latter despite calibration to the first WHO SARS‐CoV‐2 antibody international standard. 19 Moreover, the correlation between antibody levels quantitated by S‐targeting antibody assays and virus neutralizing antibody titers (NtAb) may differ notably across immunoassays.…”

Vaccine‐induced binding and neutralizing antibodies against Omicron 6 months after a homologous BNT162b2 booster

“…The administration of a homologous BNT162b2 booster dose increased the VE to 58.9% (interquartile range [IQR] = 52.7%–63.3%) within 2–4 weeks. 7 , 30 , 32 , 33 , 34 This increase was consistent with the rise of binding (median fold increase = 26.8; IQR = 13.6–51.7) 35 , 36 , 37 and neutralizing antibodies (median fold increase = 27.3; IQR = 10.2–52.7). 18 , 19 , 38 , 39 , 40 , 41 However, a waning of protection against symptomatic diseases was rapidly observed 8–14 weeks after the booster (median VE = 37.9%; IQR = 24.6%–45.1%).…”