Abstract / Summary
The COVID-19 pandemic has already been controlled with diverse vaccine platforms. Here, we evaluated antigen-specific activation-induced-cell-markers (AIM) of vaccinees and measured the duration of their activation. Vector-based (Covishield), mRNA-based (Pfizer-BioNTech/Moderna), and vero-cell (Sinopharm) vaccinees were studied over a two-year period. Peripheral blood mononuclear cells (PBMCs), isolated from the blood at different day points, were stimulated using spike-peptide of Wuhan, Beta, Delta, and Omicron variants, and we assessed helper T cell-specific AIM+ activities. We found significant expression of CD134 + CD137+ AIM-markers toward all spike-peptides, among all vaccine groups, and mRNA vaccinees induced this response with one dose of vaccine. Significant CD134 + CD40L+ expressions were observed after 1st dose of Covishield and mRNA vaccines which remained consistently elevated until one year. Notably, higher CD134 + and CD137 + expressions were found on activated (CD4 + CD69+) T cells in mRNA vaccinees throughout the one-year follow-up. Therefore, COVID-19 vaccines can generate significant helper T cell responses against viral determinants, with induction being highest for mRNA-based vaccines; suggesting such vaccine approaches could be applied against other viral pathogens in the future.