Investigation of cellular and humoral immune responses following COVID-19 vaccination in respiratory healthcare professionals

ABSTRACT

Background: SARS-CoV-2 vaccines are expected to induce both cellular and humoral immune responses, however, the dynamics and correlation between the two types of immunity are not precisely understood. Aim(s) Assessing IgG levels and T-cell response induced by SARS-CoV-2 vaccines and investigating the correlation between cellular and humoral immune responses. Method(s) Blood samples were taken from 166 respiratory healthcare professionals at four time-points first before administering the booster vaccine, then on day 28, 56 and 120 post-vaccination. For the assessment of humoral immune response anti-Spike protein IgG ELISA was used, while T-cell response was tested by interferon-gammarelease-assay. Result(s) Out of 166 patients, 120 individuals presented positive result for interferon-gamma, while 100 had positive results for IgG. The positivity rate of cellular immune response was found to be significantly higher than humoral between the second and third doses of anti-COVID vaccines (P<0,05). Participants, who have had SARS-CoV-2 infection before the first two shots, the immune response was detectable at a statistically higher rates than in the COVID naive group. The third dose triggered different dynamics regarding the IgG titers and T-cell response. Four months after the administration of the booster shot both humoral and cellular immune response were detectable simultaneously. Conclusion(s) After the first two doses, the cellular immune response was found to last longer than humoral, especially in previously infected individuals. Measuring the T-cell responses to SARS-CoV-2 vaccines may complement the antibody tests currently used in clinical practice.