Results followed a similar trend as seen with BA.1 neutralizing antibodies: the highest BA.1-specific polyfunctional CD4+ T-cell response among organ transplant recipients was seen in those recovered from Omicron-BA.1 infection (cohort 2) (p = 0.016 vs. non-Omicron variant infection; p < 0.001 vs. triple-vaccinated transplant recipients), with responses comparable to that observed in triple-vaccinated healthcare worker controls (cohort 4) (p = 0.22 vs. HCW controls). Here, CD4 is linked to infection.