Predictors of Humoral Response to SARS-CoV-2 Vaccination after Hematopoietic Cell Transplantation and CAR T Cell Therapy

Cellular therapies including allogeneic and autologous hematopoietic cell transplant (allo-HCT, auto-HCT) and chimeric antigen receptor T cell therapy (CAR T) render patients severely immunocompromised for extended periods post-therapy, and data on responses to COVID-19 vaccines are limited. We analyzed anti-SARS-CoV-2 spike IgG antibody (spike Ab) titers and neutralizing Ab among 217 recipients of cellular treatments (allo-HCT, n=149, auto HCT n=61, and CAR T n=7). At 3 months after vaccination, 188 patients (87%) had positive spike Ab levels and 139 (77%) had positive neutralization activity, compared to 100% for both in 54 concurrent healthy controls. Time from cellular therapy to vaccination and immune recovery post-cellular therapy were associated with response. Vaccination against COVID-19 is an important component of post-cellular therapy care, and predictors of quantitative and qualitative response are critical in informing clinical decisions about optimal timing of vaccines and the requirement for booster doses.