T-cell Immunity in Vaccinated Individuals
Next, we analyzed Spike-specific CD4+/CD8+ immune responses to the Pfizer BNT162b2 vaccine. We compared Spike-specific T-cell immunity to 19 healthy controls, 38 infected patients, and 38 vaccinated individuals 1 month after the 2nd vaccine dose (Figure 2B). No healthy unvaccinated individuals showed positive CD4+ T-cells against SARS-CoV-2, but infected patients and vaccinated individuals demonstrated substantial spike-specific CD4+ T-cell immunity: 87% (33 of 38) and 89% (34 of 38) respectively. CD8+ T-cells from healthy controls, infected patients, and vaccinated individuals showed 21% (4 of 19), 34% (13 of 38), and 58% (22 of 38) positive immune responses against SARS-CoV-2 spike peptides, respectively. Therefore, the Pfizer BNT162b2 vaccine induced T-cell reactivity to Spike-specific peptides that was equivalent to that seen in infected patients after recovery.