ABSTRACT
Various immunopathological events characterize the SARS-CoV-2 infection. Nevertheless, it has been reported that T cell response against SARS-CoV-2 is predominated by CD4+ T cells, which could be related to the compromised long-lasting protection. Furthermore, different vaccines have been developed to prevent coronavirus disease 2019 (COVID-19). Therefore, this research aimed to analyze and compare Fourier transform infrared (FTIR) spectra of vaccinated people with a positive (V-COVID-19 group) or negative (V-Healthy group) qPCR test, evaluating the long-lasting immune and T-cell responses through FTIR spectroscopy. Most individuals that integrated the V-Healthy group (88.1%) were asymptomatic; contrary, only 28% of the V-COVID-19 were asymptomatic. Likewise, 68% of the V-COVID-19 group had at least one coexisting illness. About the immunological and T-cell responses analyzed through FTIR spectroscopy, the V-COVID-19 group showed a greater content of IgG and IgA as well as the analyzed cytokines (IFN-γ, TNF-α, IL-1 β, IL-6, and IL-10). Therefore, it was possible to evaluate in saliva the long-lasting immune and T-cell responses through FTIR spectroscopy, showing a statistical significance between the groups. Moreover, we corroborated that the protective role of vaccination is not only by antibodies; the vaccine-induced T cells might contribute to vaccine efficacy against viral variants.