The objectives of this study were to assess the immunogenicity and safety of COVID-19 vaccines in patients with haematological malignancy. A systematic review and meta-analysis of clinical studies of immune responses to COVID-19 vaccination stratified by underlying malignancy and published from 1 January 2021 to 31 August 2021 was conducted using MEDLINE, EMBASE and CENTRAL. Primary outcome was the rate of seropositivity following 2 doses of COVID-19 vaccine with rates of seropositivity following 1 dose, rates of positive neutralising antibody (nAb), cellular responses and adverse events as secondary outcomes. Rates were pooled from single arm studies while rates of seropositivity were compared against the rate in healthy controls for comparator studies using a random effects model and expressed as a pooled odds ratio with 95% confidence intervals. Forty-four studies (16 mixed group, 28 disease specific) with 7064 patients were included in the analysis (2331 following first dose, 4733 following second dose). Overall seropositivity rates were 61-67% following 2 doses and 37-51% following 1 dose of COVID-19 vaccine. The lowest seropositivity rate was 51% in CLL patients and was highest in patients with acute leukaemia (93%). Following 2 doses, nAb and cellular response rates were 57-60% and 40-75% respectively. Active treatment, ongoing or recent treatment with targeted and CD-20 monoclonal antibody therapies within 12 months was associated with poor COVID-19 vaccine immune responses. New approaches to prevention are urgently required to reduce COVID-19 infection morbidity and mortality in high-risk patient groups that respond poorly to COVID-19 vaccination.

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