Humoral and cellular responses after a third dose of BNT162b2 vaccine in patients treated for lymphoid malignancies

BACKGROUND Immunocompromised patients such as patients with hematological malignancies have impaired immune response to two doses of BNT162b2 (Pfizer / BioNtech) vaccine against SARS-CoV-2. Evaluation of a repeated immune stimulation with a third vaccine dose is needed. METHODS a vaccine monitoring observatory was conducted in outpatients who were treated for lymphoid malignancies (LM) to monitor both immune and cellular response measured the day of administration of the dose 3 of the mRNA vaccine BNT162b2 and again three to four weeks. Elecsys ® Anti-SARS-CoV-2 immunoassay was used to asses to the level of SARS-CoV-2 anti-Spike (S) antibodies (Abs) titer and SARS-CoV-2-specific T-cell responses were assessed by a whole blood Interferon-Gamma Release Immuno Assay (IGRA) (QuantiFERON Human IFN-gamma SARS-CoV-2, Qiagen®). RESULTS Among the 43 assessable patients (suffering from chronic lymphocytic leukemia (CLL) (n=15), indolent and aggressive B cell non-Hodgkin lymphoma (NHL) (n=14), and multiple myeloma (MM) (n=16)), 18 (41,8%) had no anti-S Abs before the dose 3 of BNT162b2 vaccine (n=9 CLL, n=8 NHL, n=1 MM), and they all 18 remained negative after the dose 3. Amongst the 25 patients with positive anti-S titers before dose 3, all patients remained positive and 23 patients increased their anti-S titer after dose 3. Patients with CLL and/or with previous anti-CD20 therapy treated within 12 months of administration of dose 3 had no significant increase of the humoral response. Among 22 available patients, dose 3 of BNT162b2 vaccine significantly increased the median IFN-gamma secretion. On eight (36.4%) patients who were double-negative for both immune and cellular response, five (22.7%) patients remained double-negative after dose 3. CONCLUSIONS Dose 3 of BNT162b2 vaccine stimulated humoral immune response among patients with LM, in particular patients with MM (who had higher anti-S baseline titer after dose 2) and those with no anti-CD20 treatment history within a year. T-cell response was increased among patients in particular with no active chemotherapy regimen. Our data support the use of an early third vaccine dose among immunocompromised patients followed for LM though some of them will still have vaccine failure.