Hematological Aspects of COVID-19

The number of COVID-19 cases worldwide has crossed 400 million cases as for February 2022. For the general population – most infected individuals suffer mild to moderate respiratory symptoms; vaccination results in immunogenicity in almost 100%; and treatment and prevention strategies are based on large randomized controlled trials. This is not the case for patients with hematological malignancies. In this special edition of Acta Haematologica, worldwide experts addressed several aspects of COVID-19 relevant for hematologists.

Alnima et al. [1] review the various aspects of COVID-19 coagulopathy, including pathophysiology, clinical and laboratory characteristics, as well as differences from disseminated intravascular coagulation. They also provide an overview of the pathophysiology of vaccine induced thrombosis and thrombocytopenia and provide available data on risk factors for this highly fatal adverse event. Currently, there are no explicit contraindications for adenovirus-based vaccines due to risk of vaccine induced thrombosis and thrombocytopenia. In addition, the authors provide a summary of current evidence of anticoagulant strategies for the management of patients with COVID-19 infection [1].

Gur et al. [2] discuss the unique clinical characteristics of COVID-19 in patients with hematological malignancy. These include a protracted disease course, with prolonged viral shedding and possibly longer infectivity. Most prolonged shedding has been described among patients treated with anti CD-20, chimeric antigen receptor T cell, or hematopoietic stem cells transplant recipients. Interactions between COVID-19 and the specific components of the immune system are described, with discussion regarding the effect of various drugs used to treat hematological malignancies [2].

Martínez et al. [3] review the outcomes of patients with hematological malignancies and COVID-19. The authors provide data on the high rates of severe disease and mortality among these patients, mostly estimated at ∼30%, with improvement over the course of the pandemic. They overview cancer-related and non-related risk factors for severe diseases and death among hematological patients. Treatment for the disease is discussed, with emphasize on interventions that might be uniquely effective for these patients, such as the administration of convalescent plasma. The authors also report data suggesting that patients with hematological malignancies may be disqualified from receiving intensive treatment; hence, treating hematologists should be alert to this possibility and clarify the baseline disease prognosis to encourage ICU care when appropriate.

Buchrits et al. [4] performed a systematic review, including all interventional randomized controlled trials evaluating currently recommended drugs to treat COVID-19. This systematic review included 22 publications, only two explicitly reported inclusion of cancer patients, and none reported outcomes specifically for this subgroup. Hence, physicians treating COVID-19 patients with hematological malignancy should be aware of the limited generalizability of data on therapeutic options for this population [4].

Immunogenicity in response to SARS-CoV-2 vaccines is descried in details by Riccardo et al. [5]. As opposed to the general population, with almost 100% humoral response to mRNA vaccines, several groups of hematological patients are less likely to develop immunogenicity to these vaccines. Patients with lymphoproliferative disorders achieve ∼40 to 50% seroconversion rates in response to mRNA. Those who were treated during the last year with anti-CD-20 agents have even lower seroconversion rates, i.e., up to 10%. Other groups with low response rates are described and include patients following chimeric antigen receptor T-cell infusion, multiple myeloma patients treated with daratumumab and hematopoietic stem cell transplant recipients during the first year after transplant [5].

Two additional, less known aspects of COVID-19 in hematological patients are discussed in this issue. Eshet et al. [6] discuss issues related to imaging of hematological patients in the era of COVID-19. Main imaging findings of COVID-19 pneumonia, with unique aspects in hematological patients, are described. Challenges in the interpretation of routine follow-up PET-CT findings during COVID-19 pandemic are discussed. These include pulmonary findings in asymptomatic or convalescing patients; reactive lymphadenopathy following disease or vaccination; increased bone marrow and spleen uptake during acute COVID; and others [6].

Yelin et al. [7] provide an overview on long COVID, detailing the clinical spectrum of this new syndrome. The review addresses on the one hand the importance of attention for symptoms that are more likely to be related to the baseline hematological malignancy and should not be disregarded as long COVID. On the other hand, the review emphasizes the recognition of long COVID symptoms as genuine and disturbing, affecting patients’ quality of life [7]. Overall, this special issue provides a broad overview of data relevant for hematologists taking care of complicated hematological malignancy patients during the time of this pandemic.