Humoral and T-cell Mediated Response after Administration of Mrna Vaccine BNT162b2 in Frail Populations.

Patients with frailty are considered to be at greater risk to get severe infection from SARS-CoV-2. One of the most effective strategies is vaccination.In our study we evaluated both the humoral immune response elicited by the vaccination at different time points, and the T-cell response in terms of interferon (IFN)-γ production in frail patients and healthy donors.Fifty-seven patients (31 patients undergoing hemodialysis and 26 HIV positive subjects) and 39 healthcare workers were enrolled. All participants received two doses of the mRNA vaccine BNT162b2.Healthcare workers showed a significantly higher antibody titer than patients twenty-one days after the first dose (p < 0.001). From the same time point we observed for both groups a decay of the antibody levels with a steeper slope of decline in the patients group. Regarding T-cell response the only significant difference between non-reactive and reactive subjects was found in median antibody levels, higher in the responders group than in non-responders.The healthcare workers seem to better respond to the vaccination in terms of antibodies production; the lack of T-cell response in about 50% of the participants seems to suggest that in our study population both humoral and cell-mediated response decline over time remarking the importance of the booster doses, particularly for frail patients.