Initial findings in patients with cancer suggest a lower seroconversion to SARS-CoV-2 vaccination possibly related to myelo-immunosuppressive therapies. We conducted a prospective study to assess factors predicting poor seroconversion and adverse events following immunisation (AEFI) to the BNT162b2 vaccine in patients on active treatment.
Cancer patients, candidates to two doses of BNT162b2 SARS-CoV-2 vaccination, were enrolled. Patients on active surveillance served as controls. The primary endpoint was poor seroconversion (anti S1/S2 IgG < 25 AU/mL) after 21 days from the second dose.
Between March and July 2021, 320 subjects were recruited, and 291 were assessable. The lack of seroconversion at 21 days from the second dose was 1.6% (95% CI, 0.4-8.7) on active surveillance, 13.9% (8.2-21.6) on chemotherapy, 11.4% (5.1-21.3) on hormone therapy, 21.7% (7.5-43.7) on targeted therapy and 4.8% (0.12-23.8) on immune-checkpoint-inhibitors (ICI). Compared to controls, the risk of no IgG response was greater for chemotherapy (p = 0.033), targeted therapy (0.005) and hormonotherapy (p = 0.051). Lymphocyte count < 1 × 10/L (p = 0.04) and older age (p = 0.03) also significantly predicted poor seroconversion. Overall, 43 patients (14.8%) complained of AEFI, mostly of mild grade. Risk of AEFI was greater in females (p = 0.001) and younger patients (p = 0.009).
Chemotherapy, targeted therapy, hormone therapy, lymphocyte count < 1 × 10/L, and increasing age predict poor seroconversion after two doses of BNT162b2 in up to 20% of patients, indicating the need for a third dose and long-term serological testing in non-responders. AEFI occur much more frequently in women and younger subjects who may benefit from preventive medications. CLINICALTRIALS.

Copyright © 2021. Published by Elsevier Ltd.