Introduction. A novel coronavirus, causing severe acute respiratory syndrome 2 (SARS-CoV-2) has spread globally since its emergence in December 2019. The mRNA SARS-CoV-2 vaccines have been proven to be an efficient and safe disease control means among adult patients without immunocompromising conditions. However, cancer patients were among the group of people that was initially excluded from the registration trials. 

Material and methods. 60 patients, enrolled to this study, had been voluntarily vaccinated either with the BNT162b2 or mRNA-1273 SARS-CoV-2 vaccine between March and June 2021 and have been undergoing systemic treatment in the Clinical Oncology Unit of the University Clinical Center of the Medical University of Silesia in Katowice, Poland. Patients received 2 injections of vaccine 21 days apart and were tested with ElecsysR Anti-SARS-CoV-2 immunoassay (Roche Diagnostics, France) for the presence of anti-S-protein antibodies in the patients’ serum. The serum samples were collected 2 to 8 weeks after receiving the second dose of vaccine. 

Results. The BNT162b2 vaccine was administered to 57 patients, while the mRNA-1273 vaccine – to 3 patients. Seroconversion was achieved in 83.33% of patients. The median amount of anti-S-protein antibodies was 75,9 U/ml.There were no statistically significant differences in terms of age between the group with seroconversion and the group without seroconversion (Mann-Whitney U-test p = 0.762). There was no statistically significant correlation between neither the BMI (Spearman test, p = 0.079) norage (Spearman test, p = 0.762) and anti-S-protein antibody levels. Just as the diagnosis (primary tumor localization), clinical stage, type of modality (chemotherapy, chemoradiotherapy, immunotherapy) and the goal of treatment (radical, palliative) were not statistically significant in terms of anti-S-protein antibody levels. 

Conclusions. Due to the high number of unresponsive or poorly responsive results, patients undergoing systemic therapy should be advised to maintain other measures of disease control such as distancing, usage of masks. Nevertheless, implementing mRNA SARS-CoV-2 vaccinesinimmunocompromised patientsduring systemic therapyis reasoned, valuable and safe.