COVID-19 Vaccine Effectiveness in Patients with Hematologic Malignancies: a Nationwide Cohort Study

BACKGROUND: In patients with hematologic malignancies, COVID-19 vaccine effectiveness is unknown and determinants of severe COVID-19 lack granularity.

METHODS: To identify determinants of SARS-CoV-2 infection outcome we conducted a population-based, nationwide cohort study, including all adult Dutch residents who tested positive for SARS-CoV-2 between June 1, 2020, and March 31, 2022. Individuals were classified as having a (history of) hematologic malignancy, solid malignancy, or no malignancies. Primary outcome was severe COVID-19, defined as COVID-19-related hospitalization or death following first SARS-CoV-2 infection.

RESULTS: Among 4 649 341 included individuals, those with hematologic malignancies were at highest risk of severe COVID-19. Vaccine effectiveness against severe COVID-19 in patients with hematologic malignancies was up to 74% (95% confidence interval, 60 to 83%), depending on the SARS-CoV-2 variant period, the number of received vaccinations, and the time interval since vaccination. Risk of severe COVID-19 was highest for patients with recently diagnosed hematologic malignancies and declined over time, except for patients with chronic hematologic malignancies. Risk of severe COVID-19 tended to be higher in patients on tumor-specific treatment such as CD38 and CD20 antibodies, proteasome inhibitors, and protein kinase inhibitors.

CONCLUSIONS: COVID-19 vaccination lowered the risk of severe COVID-19 in SARS-CoV-2-infected patients with hematologic malignancies, although these patients remained at elevated risk compared to others. Determinants of severe COVID-19 included type of malignancy, time interval between malignancy diagnosis and SARS-CoV-2 infection, and treatment. These data can guide healthcare professionals in designing additional prevention and therapeutic strategies against respiratory virus infections for patients with hematologic malignancies.