Effect of a third booster dose of COVID-19 mRNA vaccine in patients with haematological cancer after the initial two-dose vaccination - a single centre report

Novel Coronavirus SARS-CoV-2 causing COVID-19 has been subject to intensive interest since its appearance in 2019, with the risk of severe course being significantly higher for adult patients with hematological malignancy. Results on a two-dose, standard vaccination regimen in patients with hematological cancer have identified risk populations with poor vaccination outcomes (Chronic lymphocytic leukemia, anti-CD20 treatment, etc.). Thus, a booster dose was anticipated with hopes of inducing an immune response in formerly non-respondent individuals. We have vaccinated 394 patients with hematological cancer with the third dose of the mRNA BNT 162b2 COMIRNATY vaccine. Our results show promise, especially for increasing protective antibody levels in patients who retain valid antibody titers. We also identify problematic populations such as chronic lymphocytic leukemia, which still represent a major challenge for prophylaxis and protection against a severe course of COVID-19. Our report brings more insight into vaccination results and behavior. Importantly, we have identified risk groups in which poor outcomes can be anticipated and what extensive preventive measures should be undertaken to avoid COVID-19 infection.