Commercial Interferon-gamma release assay to assess the immune response to first and second doses of mRNA vaccine in previously COVID-19 infected versus uninfected individuals

•We assessed antibodies and T cell response in a cohort with previous COVID-19 or not.•CD4+ and CD8+ T cells were determined with an easy-to-perform IGRA commercial assay.•Previous infected individuals experienced antibodies and T-cell booster after first dose.•Immune response in previously infected did not differ between first and second doses.•The elderly showed higher response in the previously infected, unlike the naïve group. We analysed immunological response during vaccination by using quantitative anti-spike IgG antibodies (qAbs) and Interferon-gamma (IFNγ) production by SARS-CoV-2-specific CD4+ and CD8+ T cells (QuantiFERON® assay). Blood samples were collected at four time points: a day before the reception of first (T0) and second (T1) BNT162b2 doses, 14 (T2) and 28 days (T3) after second dose. Fifty individuals were included: 34 previously infected by SARS-CoV-2 (CoV2+) and 16 that were not (CoV2-). Among CoV2+, we only observed significant differences after the first dose in both qAbs and IFNγ+ T cells. CoV2- showed differences after each dose, and the response was lower than CoV2+. Older people presented a higher response in CoV2+, while in CoV2, young people responded best. Our results suggest that the second BNT162b2 vaccine dose is not a priority in people with previous COVID-19. QuantiFERON® is a good option to monitor T-cell immunity to SARS-CoV-2.