Antibodies anti-SARS-CoV2 time-course in patients and vaccinated subjects: an evaluation of the harmonization of two different methods

Abstract

AbstractThe time-course of antibodies anti SARS-CoV2 is not yet well elucidated, especially in people who underwent a vaccination campaign. In this study we measured antibodies anti-S1 and anti-RBD with two different methods both in patients and in vaccinated subjects.108 specimens from 48 patients diagnosed as COVID-19 affected (time from the onset of symptoms from 3 to 368 days) and 60 specimens from 20 vaccinated subjects (collected after 14 days from the first dose, 14 days and 3 months after a second dose of Comirnaty) were evaluated.We used an ELISA method that measure IgG against anti-Spike 1 and a chemiluminescence immunoassays that measure IgG anti-RBD.In the patients, antibodies concentrations tend to decline after a few months with both methods, but persist relatively high up to nearly a year after symptoms.In vaccinated subjects, antibodies were already detectable after the first dose, but after the booster they show a significant increase. However, the decrease is rapid, given that after 3 months after the second vaccination they are reduced to less than a quarter.The conversion of the results into BAU units improves the relationship between the two methods. However, in vaccinated subjects there was no evidence of proportional error after the conversion, while in the patients the difference between the two methods remained significant.