• Ioannis P Trougakos, Evangelos Terpos, Christina Zirou, Aimilia D Sklirou, Filia Apostolakou, Sentiljana Gumeni, Ioanna Charitaki, Eleni-Dimitra Papanagnou, Tina Bagratuni, Christine-Ivy Liacos, Andreas Scorilas, Eleni Korompoki, Ioannis Papassotiriou, Efstathios Kastritis, and Meletios A Dimopoulos.
• Department of Cell Biology and Biophysics, Faculty of Biology, National and Kapodistrian University of Athens, Athens, Greece. itrougakos@biol.uoa.gr.
• Bmc Med. 2021 Aug 23; 19 (1): 208.

BackgroundCoronavirus SARS-CoV-2, the causative agent of COVID-19, has caused a still evolving global pandemic. Given the worldwide vaccination campaign, the understanding of the vaccine-induced versus COVID-19-induced immunity will contribute to adjusting vaccine dosing strategies and speeding-up vaccination efforts.MethodsAnti-spike-RBD IgGs and neutralizing antibodies (NAbs) titers were measured in BNT162b2 mRNA vaccinated participants (n = 250); we also investigated humoral and cellular immune responses in vaccinated individuals (n = 21) of this cohort 5 months post-vaccination and assayed NAbs levels in COVID-19 hospitalized patients (n = 60) with moderate or severe disease, as well as in COVID-19 recovered patients (n = 34).ResultsWe found that one (boosting) dose of the BNT162b2 vaccine triggers robust immune (i.e., anti-spike-RBD IgGs and NAbs) responses in COVID-19 convalescent healthy recipients, while naïve recipients require both priming and boosting shots to acquire high antibody titers. Severe COVID-19 triggers an earlier and more intense (versus moderate disease) immune response in hospitalized patients; in all cases, however, antibody titers remain at high levels in COVID-19 recovered patients. Although virus infection promotes an earlier and more intense, versus priming vaccination, immune response, boosting vaccination induces antibody titers significantly higher and likely more durable versus COVID-19. In support, high anti-spike-RBD IgGs/NAbs titers along with spike (vaccine encoded antigen) specific T cell clones were found in the serum and peripheral blood mononuclear cells, respectively, of vaccinated individuals 5 months post-vaccination.ConclusionsThese findings support vaccination efficacy, also suggesting that vaccination likely offers more protection than natural infection.© 2021. The Author(s).

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