Using the largest national cohort of COVID-19 cases and controls, researchers attempted to learn more and gather real-world evidence on the risks and outcomes of breakthrough COVID-19 infections in cancer patients who were vaccinated.

According to a study published in the Journal of Clinical Oncology, researchers revealed that patients with cancer have a greater risk for developing breakthrough infections and severe outcomes. In the study, researchers utilized data from the National COVID Cohort Collaborative to identify breakthrough infections between December 1, 2020, through May 31, 2021, among more than 64,000 patients partially or fully vaccinated with mRNA COVID-19 vaccines and with no documentation of prior severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection.

The researchers identified 6,860 breakthrough cases. Of those cases, 1,460 (21.3%) were patients with cancer. There was a significantly greater risk for breakthrough infection with solid-tumor and hematologic malignancies (odds ratios [ORs], 1.12, and 4.64, respectively) and severe outcomes (ORs, 1.33, and 1.45, respectively) versus noncancer patients when adjusting for age, gender, race/ethnicity, smoking status, vaccine type, and vaccination date.

Patients with hematologic malignancies had an expanded risk for breakthrough infections (adjusted OR range from 2.07 for lymphoma to 7.25 for lymphoid leukemia) compared with solid tumors. Breakthrough risk was diminished after the second vaccine dose for all cancers (OR = 0.04; 95% CI, 0.04-0.05) and for Moderna's mRNA-1273 compared with Pfizer's BNT162b2 vaccine (OR = 0.66; 95% CI, 0.62-0.70), particularly in patients with multiple myeloma (OR = 0.35; 95% CI, 0.15-0.72). Moreover, medications with major immunosuppressive effects and bone marrow transplantation were strongly correlated with breakthrough risk among the vaccinated population.

The authors concluded that patients with cancer—particularly those with hematologic malignancies—are at a heightened risk for developing breakthrough infections and severe outcomes. They also noted that oncology patients with vaccination were at significantly decreased risk for breakthrough infections, and further research is required to evaluate boosters and new SARS-CoV-2 variants.

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