2341. Response to Vaccination Against COVID-19 in a Community Oncology Practice: a Rational for Antibody Testing

BACKGROUND: Patients with cancer are at increased risk of morbidity and mortality from COVID-19. Vaccination is crucial to prevent this potentially fatal infection. The aim of this study was to evaluate the seroconversion rate in response to 3 different COVID-19 vaccines in patients with cancer in a community setting. METHODS: In this retrospective cohort study, we included 136 patients of a community oncology clinic with solid and hematological malignancies, fully vaccinated against SARS-CoV-2 and without a history of COVID-19. We evaluated qualitative seroconversion rates against the SARS-CoV-2 spike protein after 2 doses and after a booster dose, and the factors associated with increased risk for lack of seroconversion. Cancer types in studied population [Figure: see text] RESULTS: The median age was 71.5 years (IQR, 64 – 79.75 years), 67 (49.3%) were receiving active treatment; 94 (69.1%) patients had a hematological malignancy, 38 (27.9%) had a solid malignancy, and 4 (2.9%) had both. Only 90 (66.2%) patients developed antibodies against the SARS-CoV-2 spike protein after initial vaccination. 53.8% of those who did not initially develop antibodies, converted after a booster dose. In a multivariable binary logistic regression, patients with hematologic malignancies were nine times more likely to not develop antibodies compared to patients with a solid malignancy or both, when controlling for age, type of COVID-19 vaccine, and cancer therapy (odds ratio [OR] 9.57; 95% confidence interval [CI] 2.65 – 34.60, p=.001). Older age was also associated with an increased risk for not developing antibodies (OR 1.07; 95% CI 1.03 – 1.11, p < .001). Antibody response after initial vaccination in each therapy group [Figure: see text] The rate of antibody production per each vaccine group (initial vaccination) [Figure: see text] The rate of antibody production in response to booster per each hematologic malignancy type [Figure: see text] CONCLUSION: In this population of patients from a community oncology clinic, older patients and patients with a hematological malignancy had an increased risk for not developing antibodies against the SARS-CoV-2 spike protein. A booster dose induced a response in a significant number of patients. DISCLOSURES: All Authors: No reported disclosures