The marginal significance at M3 ( p = 0.063), though not strong, may indicate a trend worthy of further investigation and could have clinical implications for the management of transplant patients concerning SARS-CoV-2 infection.
From M6 (six months after the second dose), which is the time of booster administration, the anti-S Ab stayed stable in the DIS/INF group ( n = 28); conversely, in NEG ( n = 265), the anti-S Ab started an increasing trend, with 57% [CI: 51–63], 74% [CI: 51–63], and 78% [CI: 71–84] of patients with an anti-S Ab titer over the positivity threshold at 6, 9, and 12 months after the second dose, respectively ( Figure 1 ).