e18603 Background: Cancer patients (pts) were among the first to receive vaccination against SARS-CoV-2 (vac). However, their attitude towards as well as experience with vac remain unclear. Methods: Between 04-11/2021 cancer pts at our university cancer center completed a baseline (BL) and follow-up (FU) questionnaire (Q) containing multiple choice questions and ten eleven-level Likert items ranging from 1 (“totally disagree”) to 11 (“totally agree”). Data was analyzed using Student’s t-test or Chi-square test. Results: 219 pts (43% female) completed BLQ (110 FUQ). Mean age was 64 (24-87) years. 82% had solid tumors, 93% were on active therapy (80% chemotherapy). 4% had history of COVID-19. 78% had already received at least one vac at BL, mainly BNT162b2 (91%) or ChAdOx1-S (8%). Only 1% refused vac. Most pts completely agreed to “definitely get vaccinated” (82%) and completely disagreed with “vac is dispensable due to COVID-19 being no serious threat” (82%; more dissent among men, p = 0.037) or “being against vaccination in general” (81%). Self-assessment as member of a risk group (p = 0.03) and fear of COVID-19 (p = 0.002) were more common among women. Every third patient (31%) completely agreed to “being afraid of COVID-19”, every second thinks “SARS-CoV-2 infection would be very dangerous” (56%). Only 41% expressed “complete confidence in the vaccine being safe” and 37% “not being afraid of side effects”. Fear of side effects (SE) was more common among women (p = 0.0016), pts with solid tumors (p = 0.05), with GI tumors (p < 0.0001) and below mean age (p = 0.006). The latter expressed less “confidence in the vaccine being safe” (p = 0.0029). At FUQ, most pts (91%) reported their vac to be well tolerated, 44% reported no SE, especially men (p = 0.001) and pts above age average (p = 0.002). Most common SE was local pain at injection site (36%), which was more frequent among women (p = 0.002), younger pts (p = 0.024) and pts with solid tumors (p = 0.04). Other common SE included fatigue (18%) and myalgia (8%). No thromboembolic events occurred. Only 3 pts had their therapy postponed due to SE. Almost all pts felt retrospectively sufficiently informed about vac and possible SE (94%), would have it again (88%) and agree to get it yearly, if recommended (78%). After vac, pts felt safe meeting friends or family (91%) or shopping (62%). Vacation (32%), work (22%), public transport (21%) or sports (19%) were considered less safe (less frequent among men, p < 0.05). Most pts (70%) did not feel that the COVID-19 pandemic negatively influenced their treatment and regarded the hospitals protective measures as adequate (91%). Conclusions: Willingness to get vac is high among cancer pts and vac is well tolerated in this sensitive cohort. However, concerns about vac safety remain an issue. Those as well as gender differences need to be addressed to increase vac rates and tolerability. The present results may help identify pts that benefit from more detailed pre-vac consultation.

Purpose Refusal to receive SARS-CoV-2 vaccination poses a threat to fighting the COVID-19 pandemic. Little is known about German cancer patients’ attitude towards and experience with SARS-CoV-2 vaccination. Methods Patients were enrolled between 04–11/2021. They completed a baseline questionnaire (BLQ) containing multiple choice questions and Likert items ranging from 1 (“totally disagree”) to 11 (“totally agree”) regarding their attitude towards vaccination and COVID-19. A follow-up questionnaire (FUQ) was completed after vaccination. Results 218 patients (43% female) completed BLQ (110 FUQ; 48% female). Most patients agreed to “definitely get vaccinated” (82%) and disagreed with “SARS-CoV-2 vaccination is dispensable due to COVID-19 being no serious threat” (82%; more dissent among men, p = 0.05). Self-assessment as a member of a risk group (p = 0.03) and fear of COVID-19 (p = 0.002) were more common among women. Fear of side effects was more common among women (p = 0.002) and patients with solid or GI tumors (p = 0.03; p < 0.0001). At FUQ, almost all (91%) reported their vaccination to be well tolerated, especially men (p = 0.001). High tolerability correlated with confidence in the vaccine being safe (r = 0.305, p = 0.003). Most patients would agree to get it yearly (78%). After vaccination, patients felt safe meeting friends/family (91%) or shopping (62%). Vacation (32%) or work (22%) were among others considered less safe (less frequent among men, p < 0.05). Conclusion Acceptance of SARS-CoV-2 vaccination is high and it is well tolerated in this sensitive cohort. However, concerns about vaccine safety remain. Those and gender differences need to be addressed. Our results help identify patients that benefit from pre-vaccination consultation.

Purpose The SARS-CoV-2 Omicron variant of concern (VOC) and subvariants like BQ.1.1 demonstrate immune evasive potential. Little is known about the efficacy of booster vaccinations regarding this VOC and subvariants in cancer patients. This study is among the first to provide data on neutralizing antibodies (nAb) against BQ.1.1. Methods Cancer patients at our center were prospectively enrolled between 01/2021 and 02/2022. Medical data and blood samples were collected at enrollment and before and after every SARS-CoV-2 vaccination, at 3 and 6 months. Results We analyzed 408 samples from 148 patients (41% female), mainly with solid tumors (85%) on active therapy (92%; 80% chemotherapy). SARS-CoV-2 IgG and nAb titers decreased over time, however, significantly increased following third vaccination (p < 0.0001). NAb (ND50) against Omicron BA.1 was minimal prior and increased significantly after the third vaccination (p < 0.0001). ND50 titers against BQ.1.1 after the third vaccination were significantly lower than against BA.1 and BA.4/5 (p < 0.0001) and undetectable in half of the patients (48%). Factors associated with impaired immune response were hematologic malignancies, B cell depleting therapy and higher age. Choice of vaccine, sex and treatment with chemo-/immunotherapy did not influence antibody response. Patients with breakthrough infections had significantly lower nAb titers after both 6 months (p < 0.001) and the third vaccination (p = 0.018). Conclusion We present the first data on nAb against BQ.1.1 following the third vaccination in cancer patients. Our results highlight the threat that new emerging SARS-CoV-2 variants pose to cancer patients and support efforts to apply repeated vaccines. Since a considerable number of patients did not display an adequate immune response, continuing to exhibit caution remains reasonable.