Cellular immunity against SARS-CoV-2 depends on the serological status

We enrolled a cohort of ostensibly healthy healthcare workers of the Pederzoli Hospital in Peschiera del Garda (Verona) who had previously received a complete primary vaccination cycle and a single homologous booster with the monovalent Pfizer/BioNTech mRNA BNT162b2 vaccine. Blood was drawn before bivalent vaccine administration. Cellular immunity was assayed with Elecsys IGRA SARS-CoV-2 test while serostatus was measured with anti-SARS-CoV-2 antibodies. The median IGRA value was significantly higher in seropositive (0.66 IU/mL) than in seronegative subjects (0.36 IU/mL). Sex (p=0.514), age (p=0.465) and time since the last vaccine dose (p=0.057) were similar between these two cohorts. In multivariable analysis, anti-SARS-CoV-2 N/S IgG seropositivity (p=0.001), but not sex (p=0.946), age (p=0.622) or time since the last vaccine dose (p=0.772), significantly predicted IGRA values. These results suggest that the SARS-CoV-2 serostatus may be a significant and independent predictor of cellular immunity.