Haematological cancers and the risk of severe COVID-19: Exploration and critical evaluation of the evidence to date.

From the outset of the COVID-19 pandemic, patients and healthcare professionals have been concerned that a history of haematological malignancy will lead to an increased risk of severe COVID-19. This led to the UK government advising patients with blood cancers to shield, massive re-organisation of NHS haematology and cancer services, and changes in treatment plans for thousands of patients. Given the unknown effects that relaxation of social-distancing measures will have on the infection rate, we review the evidence to date to see whether a history of haematological malignancy is associated with increased risk of COVID-19. Multivariable analysis of large population studies, taking other known risk factors into account, do indicate that patients with haematological malignancy, especially those diagnosed recently, are at increased risk of death from COVID-19 compared to the general population. The evidence that this risk is higher than for those with solid malignancies is conflicting. There is suggestive evidence from smaller cohort studies that those with myeloid malignancy may be at increased risk within the blood cancer population, but this needs to be confirmed on larger studies. Ongoing large collaborative efforts are required to gain further evidence regarding specific risk factors for severe complications of COVID-19.