Outcomes of Breakthrough COVID-19 Infections in Patients with Hematologic Malignancies.

Patients with hematologic malignancies have both an increased risk for SARS-CoV2 infections and higher morbidity/mortality. They have lower seroconversion rates post-vaccination, potentially leading to inferior COVID-19 outcomes, despite vaccination. We consequently evaluated the clinical outcomes of COVID-19 infections in 243 vaccinated and 175 unvaccinated patients with hematologic malignancies. Hospitalization rates were lower in the vaccinated group when compared to the unvaccinated group (31.3% vs 52.6%, p≤0.001). However, the rates of COVID-associated death were similar at 7.0% and 8.6% in vaccinated and unvaccinated patients, respectively (p=0.61). By univariate logistic regression, females (odds ratio (OR) 2.77, p=0.01), older patients (OR 1.03, p=0.02), and individuals with higher modified Charlson Co-morbidity Index scores (OR 1.32, p=0.003) were at a higher risk of death from COVID-19 infections. To account for the non-randomized nature of COVID-19 vaccination status, a propensity score weighting approach was utilized. In the final propensity weighted model, vaccination status was not significantly associated with the risk of death from COVID-19 infections (OR 0.70, p=0.36) but associated with the risk of hospitalizations (OR 0.38, p<0.001). The predicted benefit of vaccination was an absolute decrease in the probability of death and hospitalization from COVID-19 infections by 2.3% and 22.9%, respectively. In conclusion, COVID-19 vaccination status in patients with hematologic malignancies was associated with a decreased risk of hospitalization but not associated with a decreased risk of death from COVID-19 infections in the pre-Omicron era. Protective strategies, in addition to immunization, are warranted in this vulnerable patient population.