ABSTRACT To investigate immune checkpoint inhibitors (ICIs) induced pancreatic injury (ICIPI), the prognostic effect of COVID-19 vaccine on cancer patients, and whether COVID-19 vaccine increases the incidence of ICIPI. We conducted a retrospective study of 256 stage IV cancer patients treated with ICIs at The First Affiliated Hospital of Anhui Medical University from January 2020 to November 2022. Data collected included pancreatic enzyme levels, treatment outcomes, and vaccination status. Statistical significance was determined using the χ2 test and Kaplan-Meier method (p < .05). Compared to the control group, the vaccinated group (p < .0001) and the group with elevated pancreatic enzyme levels (p = .044) demonstrated higher disease control rates, indicating a direct benefit of vaccination and enzyme monitoring on treatment outcomes. Additionally, vaccinated patients demonstrated longer overall survival versus unvaccinated patients (23.9 months [95% CI, 22.3–25.5] vs 23.6 months [95% CI, 21.1–26.2], HR = 0.45 [95% CI, 0.24–0.86], p = .015) and progression-free survival (17.2 months [95% CI, 14.3–20.1] vs 13.7 months [95% CI, 11.3–16.1], HR = 0.54 [95% CI, 0.36–0.82], p = .004). Importantly, the analysis revealed no significant association between vaccination and pancreatic injury (p = .46). Monitoring pancreatic enzymes can effectively evaluate the therapeutic impact in patients using ICIs. Patients vaccinated against COVID-19 experience better immunotherapy outcomes without an increased risk of ICIPI.