Abstract
Patients receiving targeted cancer treatments such as tyrosine kinase inhibitors (TKIs) have been classified in the clinically extremely vulnerable group to develop severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), including patients with chronic myeloid leukaemia (CML) taking TKIs. In addition, concerns that immunocompromised individuals with solid and haematological malignancies may not mount an adequate immune response to a single dose of SARS-CoV-2 BNT162b2 (Pfizer-BioNTech) vaccine have been raised. In the present study, we evaluated humoral and cellular immune responses after a first injection of BNT162b2 vaccine in 16 patients with CML. Seroconversion and cellular immune response before and after vaccination were assessed. By day 21 after vaccination, anti-Spike immunoglobulin G was detected in 14/16 (87·5%) of the patients with CML and all developed a neutralising antibody response [serum dilution that inhibits 50% infection (ID50 ) >50], including medium (ID50 of 200-500) or high (ID50 of 501-2000) neutralising antibodies titres in nine of the 16 (56·25%) patients. T-cell response was seen in 14/15 (93·3%) evaluable patients, with polyfunctional responses seen in 12/15 (80%) patients (polyfunctional CD4+ response nine of 15, polyfunctional CD8+ T-cell response nine of 15). These data demonstrate the immunogenicity of a single dose of SARS-CoV-2 BNT162b2 vaccine in most patients with CML, with both neutralising antibodies and polyfunctional T-cell responses seen in contrast to patients with solid tumour or lymphoid haematological malignancies.