e18732 Background: Autologous stem cell transplant (ASCT) is standard therapy for patients (pts) with multiple myeloma (MM), yet the risks of such treatment include neutropenic fever (NF) and bacteremia. Fluoroquinolones (FQs) are a mainstay of bacterial prophylaxis (ppx) of NF in ASCT at many transplant centers and reduce the incidence of bacteremia. Nevertheless, ppx regimens for ASCT are not standardized and variability exists even within single institutions. While antibacterial ppx decreases infections, antibiotic use can also cause toxicity, resistance, and microbiome disturbance. The addition of doxycycline (doxy) to FQs was previously linked to reduced NF and bacteremia when utilized for ppx in MM pts at our institution, leading some providers to incorporate doxy into their ppx regimens. However, our prior study introduced multiple confounders, including differing pre-transplant conditioning regimens between ppx groups. We sought to further compare the incidence of NF and bacteremia in MM pts receiving ppx with FQ alone and FQ-doxy during a time when ppx strategies varied but transplant conditioning was consistent between groups. Methods: This is a single institution retrospective review. We analyzed all medical charts in the ASCT database of MM pts treated at our institution between Jan 2016 and Dec 2021. The primary objective was to determine the effect of bacterial ppx on the rate of NF and bacteremia within 30 days of ASCT. Data was also collected on several pt characteristics. Results: Out of 341 pts with MM who underwent ASCT following melphalan (mel) conditioning, 121 received FQ (ciprofloxacin or levofloxacin) ppx and 220 received FQ-doxy ppx. Pt characteristics and outcomes of interest are shown in Table 1. NF developed in 71 (58.7%) and 103 (46.8%) pts in the FQ and FQ-doxy groups, respectively (p = 0.042). The odds of NF in FQ-doxy compared to FQ is 0.62 (95% CI 0.4, 0.97). Bacteremia developed in 7 (5.8%) and 6 (2.7%) pts of the FQ and FQ-doxy groups (p = 0.235). The odds of bacteremia in FQ-doxy compared to FQ is 0.46 (95% CI 0.15, 1.39). Documented bacteremia was infrequent, yet resistance profiles demonstrated FQ-resistant E. coli strains in the 7 total Gram-negative bacteremia cases and 5 extended-spectrum beta-lactamases. Conclusions: Overall, there were fewer cases of NF in the FQ-doxy ppx group than FQ, however there was no significant difference in the cases of bacteremia. This finding does not support the addition of doxy to FQ ppx at our institution and a future randomized controlled trial investigating appropriate ppx for ASCT is warranted. [Table: see text]

134 Background: Cancer(ca) and old age are risk factors for developing severe COVID-19 (C19+) disease, related morbidity and mortality. These patients (pts) were excluded from clinical trials evaluating the safety and efficacy of 3 FDA approved C19 vaccines (vax). Genitourinary (GU) ca-prostate, bladder and kidney ca contribute to the majority of non-skin ca and median age of these pts range from 65-75 yrs. We aimed to study these highly vulnerable pts behavior and outcomes regarding C19 vax in comparison to non-GU ca pts (18-89 years). Methods: A prospective and observational single center study. Adult ca pts seen in clinics from Nov 2021-Sept 2022 were randomly interviewed using telephone surveys after a verbal consent. Type of ca and therapy data were collected from pts’ medical records. The survey included C19 disease status, vax status positive (+) or negative (-), reason for vax status, side effects (s.e), impact on ca Rx or ca progression. Data was entered on REDCap. The primary end point was rate of vaccination in adult ca pts. Secondary end points were to quantify C19 vax acceptance vs. hesitance, identify s.e of C19 vax and effect of C19 vax on outcomes in GU and non-GU Ca pts. Results: N=172; GU ca 21 (12.2%) and non-GU ca 151 (87.8%). Among GU ca pts- 9 had prostate ca, 7 had bladder ca and 5 had renal ca. C19+ in 4 (19%) GU and 45 (30.2%) non-GU pts. GU pts: 90.5% received C19 vax (Pfizer 47.6%; Moderna 42.9%, J & J 0%); 9.5% were not vaxed. Non-GU pts: 85.2% received C19 vax (Pfizer 39.1%; Moderna 43%, J & J 2.6%); 14.8% were not vaxed. The top 3 risk factors for serious C19+ were age >65yr (76.2%), heart disease (61.9%) and BMI>30 (42.9%) in GU ca pts and age >65yr (46.4%), BMI>30 (35.1%) and smoking (19.9%) in non-GU ca pts. The top 3 reasons for C19 vax (+) in GU ca pts: protection against C19+ for self (81%), for others (47.6%) and provider recommendation (38.1%). The main reasons for vax hesitancy in C19 vax (-) GU ca pts: concern for allergy to the vax (4.8%) and prior C19 infection (4.8%). The common s.e of C19 vax reported in GU ca pts were injection site inflammation (19%), headache (4.8%), muscle/body aches (4.8%) but no lymphadenopathy. None of GU ca pts reported delay in Rx or progression of the disease due to C-19 vax. Conclusions: C19 vax were overall well tolerated and did not impact ca outcomes in pts with GU malignancies. Oncologists should discuss the importance of C19 vax in the context of ca. Clinical trial information: NCT04953065 . [Table: see text]

e18897 Background: COVID‐19 (C19) disproportionately affects those with comorbid medical conditions, leading to significantly higher mortality rate. Cancer(ca) is a well-studied risk factor for developing severe C19 disease. However, ca patients (pts) were largely excluded from clinical trials evaluating the safety and efficacy of 3 FDA-approved C19 vaccines (vax). We aim to study this highly vulnerable pts’ behavior and outcomes regarding C19 vax. Methods: A prospective and observational single center study. Adult ca pts (18-89 years) seen in clinics from Nov 2021-Sept 2022 were randomly interviewed using telephone surveys after a verbal consent. Type of ca and therapy data were collected from pts’ medical records. The survey included C19 disease status, vax status positive (vax+) or negative (vax-), reason for vax status, s.e, impact on ca Rx or ca progression. Our primary objectives were to assess the rate of vaccination in the adult ca pts and identify barriers to vaccination. Secondary objectives were determining factors associated with vax acceptance vs. hesitancy, identifying s.e of C19 vax, and effect of C19 vax on clinical outcomes in ca pts. Results: N = 170 [Males 82 (48.2%) and females 88 (51.8%)]. The median age was 65 years. Among 170 pts, 58.2% had solid malignancy, 40% had hematologic malignancy, and 1.8% had both solid and hematologic malignancy. Refer to Table 1 for outcomes data. Overall, 146 (85.9%) pts received C19 vax. C19 infection positive (C19+) in 49 (28.8%) pts. Of them 9 (18.4%) pts required hospitalization. The vax rate of prior C19+ pts was 73.5% compared to 90.9% in C19 infection negative (C19-) pts (p = 0.0013). Demographic factors were not significantly associated with vaccine uptake. A total of 50% pts developed s.e from vax. However only one patient (0.68%) reported a delay in ca treatment due to C19 vax and believed that vax affected the ca outcome. Conclusions: Our results demonstrate that majority of the ca pts were vaccinated against C19 and tolerated it well, with minimal side effects. Prior C19 infection significantly decreased vax uptake. Vaccination did not have notable adverse effect on ca outcomes. Oncologists should discuss the importance of C19 vax in the context of ca to avoid misconceptions and hesitancy. Clinical trial information: NCT04953065 . [Table: see text]