PROS1 and Decreased total B cell count: Interestingly, among the 36 patients with a T-cell response directed against the S protein, 17 did not achieve a protective anti-S IgG level (≥ 3100 UA/mL) after the second BNT162b2 inoculum, including 15 with impaired B-cell status (B-cell lymphopenia, n = 12 or active CLL n = 3), suggesting that immunity to vaccine was not completely abrogated in these patients.