ABSTRACT
Real-world data regarding the effectiveness, safety and immunogenicity of the Pfizer-BioNTech BNT162b2 mRNA vaccine are accumulating in the literature, suggesting that this vaccine generates high titres of S1-binding IgG antibodies that exhibit potent virus neutralization capacity. This is the first phase IV immunogenicity study to recruit a large number of Greek healthcare workers (n=425) including 63 previously-infected subjects. We measured titres of neutralizing IgGs against the receptor-binding domain of the S1 subunit of the spike protein of SARS-CoV-2 14 days post-immunization with the first dose, employing the SARS-CoV-2 IgG II Quant assay. A total of 92.24â% of our study cohort received a positive assay outcome and titres varied with age. Post-hoc analysis revealed that although titres did not significantly differ among participants aged 20-49 years, a significant decline was marked in the age group of 50-59 years, which was further accentuated in subjects aged over 60. Antibody titres escalated significantly among the previously-infected, indicating the potential booster effect of the first dose in that group.
Subject(s)
COVID-19 Vaccines/immunology , COVID-19/prevention & control , Health Personnel , Immunogenicity, Vaccine , SARS-CoV-2/immunology , Adult , Aged , BNT162 Vaccine , COVID-19/diagnosis , COVID-19/virology , COVID-19 Vaccines/administration & dosage , Female , Greece/epidemiology , Humans , Male , Middle Aged , Outcome Assessment, Health Care , ROC Curve , Vaccination , Young AdultABSTRACT
This study monitored titers of neutralizing IgG against the receptor-binding domain of the SARS-CoV-2 S1 subunit 14 days post-injection of each dose of the BNT162b2 mRNA Covid-19 vaccine in 401 Greek healthcare workers aged 20-67. After the first dose, titers varied upon age and history of infection, being lower in the 50+ age group and significantly higher among the seropositive. After the second dose, immunogenicity was significantly boosted in the age 50+ and SARS-CoV-2-naïve individuals, indicating the effectuality of its timely administration, yet questioning its value among the seropositive.