Usefulness of IVD Kits for the Assessment of SARS-CoV-2 Antibodies to Evaluate the Humoral Response to Vaccination

Abstract

Background: The introduction of the vaccination against SARS-CoV-2 infection creates the need for precise tools for the quality control of vaccination procedures, detection of poor humoral response, and estimation of the achieved protection against the disease. Thus, the study aimed to compare the results of the anti-SARS-CoV-2 tests to evaluate the application of the WHO standard unitage (the binding antibody units; BAU/mL) for a measurement of response to the vaccination. Methods: Patients undergoing vaccination against SARS-CoV-2 with Pfizer/BioNTech BNT162b2 (BNT162b2) (n = 79), referred for SARS-CoV-2 antibody measurement prior to vaccination and 21 days after dose 1, and 8, 14, and 30 days after dose 2 were included. The sera were tested with three assays: Elecsys SARS-CoV-2 S (Roche), LIAISON® SARS-CoV-2 TrimericS IgG (DiaSorin), and SARS-CoV-2 IgG II Quant (Abbott). Results: The three assays showed varying correlations at different time points in the study. The overall agreement for all samples was moderate to high (ρ = 0.663–0.902). We observed the most uniform agreement for the day of dose 2 (ρ = 0.775–0.825), while it was least consistent for day 8 (ρ = −0.131–0.693) and 14 (ρ = −0.247–0.603) after dose 2. The dynamics of changes of the SARS-CoV-2 antibody levels in patients without history of prior SARS-CoV-2 infection appears homogenous based on the Roche results, more heterogenous when considering the DiaSorin results, and in between for the Abbott results. Conclusions: The results highlight the need for further work on the international standard of measurement of SARS-CoV-2 Ig, especially in the era of vaccination. The serological assays can be useful to detect IgG/IgM antibodies to assess the response to the vaccination. However, they cannot be used interchangeably. In terms of the evaluation of the immune response to the BNT162b2 vaccine, Roche and Abbott kits appear to be more useful.

The comparability of Anti-Spike SARS-CoV-2 antibody tests is time-dependent: a prospective observational study

“…This hypothesis is also supported by the observation that in direct comparison with the sVNT, the Roche assay underestimated inhibitory capacities at week 3 (Figure 4), which is discussed in detail below. Thus, overall, the assays studied show significant differences in the kinetics of antibody levels, which has been reported previously but was only rarely demonstrated from the same sample with different assays 28,67 . Although the correlation between Roche and Abbott improved over time, their relationship changed significantly depending on the time of blood sampling (Figure 3).…”

B Cell Composition Is Altered After Kidney Transplantation and Transitional B Cells Correlate With SARS-CoV-2 Vaccination Response

“…Respective values had to be converted to International Standard units for comparison, as recommended by the WHO (74). Though, it is still a matter of debate whether results from different platforms may be used interchangeably (75,76). We dichotomized the outcome of antibody testing into responders and non-responders, according to the detectability of specific antibodies, with the rationale, that even a minimal response may offer a crude measure of protection.…”

Humoral Response after Vaccination with Half-Dose of BNT162b2 in Subjects under 55 Years of Age

“…However, the data already available show that it correlates with measured levels of binding antibodies [35,36]. Although research on the WHO International Standard introduced the goal of standardizing the results obtained with different SARS-CoV-2 antibody assays and correlating their level with the neutralizing effect, this has not been confirmed in previous studies [13,23]. The dangers of new mutations escaping the neutralizing properties of antibodies formed both after COVID-19 and after vaccination, should be the impetus to vaccinate the maximum possible proportion of the population as soon as possible, to obtain the maximum possible neutralizing antibody levels in that population.…”

“…The test results are reported in units per mL (U/mL) and can be converted to the WHO standard, defined as Binding Antibody Units per mL (BAU/mL), by multiplying the Roche result by 1.029, according to the manufacturer. As suggested previously [13], the identifiers should be added to the unit designation to show what is being measured. Therefore, for the Roche assay, we described the unit as BAU RBD-IgG+IgM /mL.…”