TY - JOUR TI - Immune response (IgG) following full inoculation with BNT162b2 COVID-19 mRNA among healthcare professionals AU - Tsatsakis, Aristidis AU - Vakonaki, Elena AU - Tzatzarakis, Manolis and AU - Flamourakis, Matthaios AU - Nikolouzakis, Taxiarchis Konstantinos and AU - Poulas, Konstantinos AU - Papazoglou, Georgios AU - Hatzidaki, Eleftheria AU - and Papanikolaou, Nikolas C. AU - Drakoulis, Nikolaos AU - Iliaki, AU - Evangelia AU - Goulielmos, Georgios N. AU - Kallionakis, Manolis and AU - Lazopoulos, Georgios AU - Kteniadakis, Stelios AU - Alegkakis, Athanasios AU - and Farsalinos, Konstantinos AU - Spandidos, Demetrios A. JO - International Journal of Molecular Medicine PY - 2021 VL - 48 TODO - 5 SP - null PB - SPANDIDOS PUBL LTD SN - 1107-3756, 1791-244X TODO - 10.3892/ijmm.2021.5033 TODO - antibody titers; SARS-CoV-2; COVID-19; vaccination; BNT162b2 COVID-19 mRNA; IgG TODO - Soon after the beginning of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic in December, 2019, numerous research teams, assisted by vast capital investments, achieved vaccine development in a fraction of time. However, almost 8 months following the initiation of the European vaccination programme, the need for prospective monitoring of the vaccine-induced immune response, its determinants and related side-effects remains a priority. The present study aimed to quantify the immune response following full vaccination with the BNT162b2 coronavirus disease 2019 (COVID-19) mRNA vaccine by measuring the levels of immunoglobulin G (IgG) titers in healthcare professionals. Moreover, common side-effects and factors associated with IgG titers were identified. For this purpose, blood samples from 517 individuals were obtained and analysed. Blood sampling was performed at a mean period of 69.0 +/- 23.5 days following the second dose of the vaccine. SARS-CoV-2 IgG titers had an overall mean value of 4.23 +/- 2.76. Females had higher titers than males (4.44 +/- 2.70 and 3.89 +/- 2.84, respectively; P=0.007), while non-smokers had higher titers than smokers (4.48 +/- 2.79 and 3.80 +/- 2.64, respectively; P=0.003). An older age was also associated with lower antibody titers (P<0.001). Moreover, the six most prevalent adverse effects were pain at the injection site (72.1%), generalized fatigue (40.5%), malaise (36.3%), myalgia (31,0%), headache (25.8%) and dizziness/weakness (21.6%). The present study demonstrated that the immune response after receiving the BNT162b2 COVID-19 mRNA vaccine is dependent on various modifiable and non-modifiable factors. Overall, the findings of the present study highlight two key aspects of the vaccination programs: First, the need for prospective immunosurveillance studies in order to estimate the duration of immunity, and second, the need to identify those individuals who are at a greater risk of developing low IgG titers in order to evaluate the need for a third dose of the vaccine. ER -