The Effect of Vaccination against COVID-19 in Cancer Patients: Final Results of the COICA Trial

Background: The COICA study is an ambispective, observational trial that was conceived to assess the clinical course of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection in cancer patients. A recently published, population-based, case-control study reported a reduced vaccine efficacy at 3-6 months in cancer patients compared to individuals without cancer. Objectives: The aim of the study was to describe coronavirus disease 19 (COVID-19) outcomes in cancer patients and analyze differences in SARS-CoV-2 outcomes between vaccinated and unvaccinated patients. Methods: Descriptive statistics and frequency counts were used to summarize characteristics of the study population. χ² test and the log-rank test were used to compare outcomes between vaccinated and unvaccinated patients. Results: A total of 141 cancer patients (80 males, 61 females) were recruited at two participating Institutions from March 2020 until April 2022 and observed from the time of positive SARS-CoV-2 test to the time of negativization or death. Approximately 35% of patients had been vaccinated at the time of infection with 2 (16 patients) or 3 (33 patients) vaccine doses. Vaccinated patients consistently and significantly showed improved COVID-19 outcomes compared to unvaccinated patients, with CT-diagnosed pneumonia, hospitalization, O₂ therapy, and death reported in 0% versus 48.6%, 2.0% versus 15.2%, 0% versus 14.1%, and 0% versus 7.6%, respectively, of assessable patients (p < 0.05). Vaccinated versus unvaccinated patients showed a significantly shorter time to negativization, with a median (95% confidence interval) time of 12 (10-14) versus 20 (17-23) days, respectively (p < 0.001). Conclusions: Vaccination consistently improved all COVID-19 outcomes. No death was recorded among vaccinated patients. Additional research is especially warranted to establish optimal timing and patient selection for administration of the fourth vaccination dose.