T‐cell response after first dose of BNT162b2 SARS‐CoV‐2 vaccine among healthcare workers with previous infection or cross‐reactive immunity

Casado, Jose L; Haemmerle, Johannes; Vizcarra, Pilar; Rodriguez‐Dominguez, Mario; Velasco, Tamara; Velasco, Hector; Centenera, Elena; Romero‐Hernandez, Beatriz; Fernandez‐Escribano, Marina; Vallejo, Alejandro

OBJECTIVES: Antibody response to the first dose of BNT162b2 SARS‐CoV‐2 is greater in COVID‐19‐convalescent than in infection‐naïve individuals. However, there are no data about T‐cell response in individuals with pre‐existing cellular immunity. METHODS: We evaluated T‐cell responses in parallel with SARS‐CoV‐2 antibody level after first dose of BNT162b2 vaccine in 23 infection‐naïve and 27 convalescent healthcare workers (HCWs) previously included in a study about humoral and T‐cell immunity. RESULTS: Overall, the antibody response was lower in the infection‐naïve group than in convalescent individuals (18 895 vs 662.7 AU mL(−1), P < 0.001), and intermediate but significantly lower in convalescent HCWs with previous negative serology (25 174 vs 1793 AU mL(−1); P = 0.015). Indeed, anti‐spike IgG titres after the first dose correlated with baseline anti‐nucleocapsid IgG titres (rho = 0.689; P < 0.001). Pre‐existing T‐cell immunity was observed in 78% of convalescent and 65% of the infection‐naïve HCWs. T‐cell response after the first dose of the vaccine was observed in nearly all the cases with pre‐existing T‐cell immunity, reaching 94% in convalescent HCWs and 93% in those with cross‐reactive T cells. It was lower in the infection‐naïve group (50%; P = 0.087) and in convalescent HCWs with negative serology (56%; P = 0.085). Notably, systemic reactogenicity after vaccination was mainly observed in those with pre‐existing T‐cell immunity (P = 0.051). CONCLUSION: Here, we report that the first dose of BTN162b2 elicits a similar S‐specific T‐cell response in cases of either past infection or cross‐reactive T cells, but lower in the rest of infection‐naïve individuals and in convalescent HCWs who have lost detectable specific antibodies during follow‐up.