The Coronavirus disease-19 (COVID-19) pandemic dramatically impacted on oncologic patients' care. Since the introduction of vaccines and the demonstration of their benefit on frail patients, COVID-19 vaccinations were indicated also for oncologic population. However, data about the impact of anticancer-treatments and the timing between vaccinations and systemic therapy de-livery were not available. We aimed to evaluate potential factors influencing the outcome of COVID-19 vaccination in cancer patients. We prospectively collected data of patients undergoing COVID-19 vaccination with gas-tro-entero-pancreatic and neuroendocrine neoplasms, treated at our Institute, between 03/2021 and 12/2021. We enrolled 46 patients, 63.1% males; at the time of data collection 86.9% received two-doses of Pfizer-BioNTech and the remains Moderna vaccine. All patients obtained a subsequent im-mune-response. A significantly lower values of IgG for patients treated with chemotherapy versus other anti-cancer agents (p=0.004). No significant effect on immune-response was reported for both vaccinations performed ≤7 vs >7 days from the last systemic treatment (p=0.77) and lymphocytes count (p=0.11). The findings suggest that the optimal timing for COVID-19 vaccination and lymphocytes count are not the issue but rather the quality of the subset of lymphocytes before the vaccination to deter-mine the efficacy level of immune-response in this population.

In our previous study of 291 cancer patients, we showed that 20% did not respond to two doses of COVID-19 vaccine administered six weeks apart. Here we investigated if psychological factors (distress, anxiety and depressive symptoms) affected antibody response and markers of vaccine activation (D-dimer) after 6 months from initial vaccination. Overall, 31 subjects (14.2%) had no antibody response at 6 months. Our analysis revealed significant predictors of vaccine failure, including stage of metastatic disease and high stress levels (OR=2.46, 95% CI, 1.05-5.77, p=0.04). Notably, nonresponders showed twice the prevalence of distress than responders (21% vs. 10%, p=0.04). Longitudinal measurements of IgG levels indicated that participants with high depressive symptoms at baseline maintained lower antibody levels over six months (p=0.003). In addition, women with high anxiety showed reduced levels of D-dimer at 6 month time (p=0.03). The data also showed that smokers and former smokers had significantly lower antibody levels than their nonsmoking counterparts (p=0.0004). At baseline, the high discomfort rate (≥5) was 34.4% in women and 23.8% in men; only men experienced an increase in median discomfort during the observation period. Moreover, higher educational level was related to increased distress among women (p=0.046). These findings underscore a critical association between elevated psychological distress and reduced immune responses to the COVID-19 vaccine, emphasizing the urgent need for targeted psychological and behavioral support within this vulnerable population.