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.

e18719 Background: An influence of various psychological factors (e.g., stress or vaccine hesitancy) on antibody response following vaccinations (vac; e.g. influenza, diphteria) has previously been reported. However, these are the first data on vaccine hesitancy’s impact on SARS-CoV-2 vac in a cohort of cancer patients (pts). Methods: Cancer pts at our university oncology center were prospectively enrolled between 01/2021-02/2022. Medical data and blood samples were collected at time of enrollment and before and after every SARS-CoV-2 vac, at 3 and 6 months. Anti-SARS-CoV-2 IgG levels and neutralizing antibodies (nAb) were determined. Pts also completed a questionnaire containing eleven-level Likert items ranging from 1 (“totally disagree”) to 11 (“totally agree”) regarding their attitude towards COVID-19 and vac in general. Results: Samples and questionnaires from 148 pts (41% female) were collected. Mean age was 64 (24-87) years. Most patients suffered from solid tumors (85%), mainly gastrointestinal (GI) cancer (59%), and were on active therapy (92%), mainly chemotherapy (80%). Agreement with “I am against vac in general” was significantly correlated with decreased SARS-CoV-2 IgG titers following first vac (ρ = -0.411, p = 0.018), second vac (ρ = -0.399, p = 0.044) and at 3 months follow-up (ρ = -0.293, p = 0.007) as well as reduced nAb after second vac (ρ = -0.533, p = 0.005) and 3 months (ρ = -0.221, p = 0.043). In contrast, stating “I will definitely get vaccinated against COVID-19” was strongly correlated with increased IgG titers following second vac (ρ = 0.44, p = 0.025). Also, “everyday stress will keep me from getting vaccinated” was significantly associated with decreased IgG and nAb following second vac (ρ = -0.433, p = 0.027; ρ = -0.391, p = 0.048). Multivariate linear regression (MLR) revealed being “against vac in general” as an independent negative predictor of IgG levels after first SARS-CoV-2 vac (β = -0.437, p = 0.022) and at 3 months follow-up (β = -0.292, p = 0.007). Among pts with GI cancer, agreement with “being afraid of vac side effects (SE)” demonstrated significantly decreased IgG (ρ = -0.334, p = 0.025) and nAb titers (ρ = -0.424, p = 0.004) after 3 months. MLR indicated fear of vac SE as an independent negative predictor of nAb after 3 months in this subgroup (β = -0.355, p = 0.025). Additionally, fear of SE was negatively correlated with anti-SARS-CoV-2 antibodies after second vac (ρ = -0.515, p = 0.029) and 3 months in male (ρ = -0.368, p = 0.011), but not in female pts. However, agreement with “I am completely confident that the vac are safe” was only correlated with increased IgG titers at 3 months follow-up in women (ρ = -0.361, p = 0.031). Conclusions: The current study revealed vaccine hesitancy’s significant negative impact on immune response following SARS-CoV-2 vac in cancer pts. Increased efforts to fight vaccine hesitancy are necessary to not only enhance vac coverage but also immune response among cancer pts.