Systemic vaccination with the BNT162b2 mRNA vaccine stimulates the humoral response.
Our study aimed to compare the intensity of the humoral immune response, measured by
SARS-CoV-2 IgG, SARS-CoV-2 IgM, and S-RBD neutralizing IgG antibody levels, after
COVID-19 vaccination versus after SARS-CoV-2 infection. We analyzed 1060 people in the
following groups: convalescents, healthy vaccinated individuals, individuals vaccinated with
Comirnaty, AstraZeneca, Moderna, or Johnson & Johnson, and vaccinated SARS-CoV-2
convalescents. The concentrations of SARS-CoV-2 IgG, SARS-CoV-2 IgM, and S-RBD
neutralizing antibodies were estimated in the oncology hospital laboratory by
chemiluminescent immunoassay (CLIA; MAGLUMI). Results: (1) We observed a rise in
antibody response in both SARS-CoV-2 convalescent and COVID-19-vaccinated groups. (2)
The levels of all antibody concentrations in vaccinated COVID-19 convalescents were
significantly higher. (3) We differentiated asymptomatic SARS-CoV-2 convalescents from the
control group. Our analysis suggests that monitoring SARS-CoV-2 IgG antibody
concentrations is essential as an indicator of asymptomatic COVID-19 and as a measure of the
effectiveness of the humoral response in convalescents and vaccinated people. Considering the
time-limited effects of post-SARS-CoV-2 infection recovery or vaccination and the
physiological half-life, among other factors, we suggest monitoring the IgG antibody level as a
criterion for the next vaccination.