Inclusion Criteria :  Group 1  Salaried staff of the Georges-François Leclerc center over 18 years old Subject vaccinated against SARS-CoV-2 for at least 1 month (last injection), AND less than 4 months (last injection). Subject who gave his consent to this study Subject affiliated to a social security scheme  Group 2  Salaried staff of the Georges François Leclerc center over 18 years old Subject not vaccinated against SARS-CoV-2 Subject having presented a proven infection by SARS-CoV-2 (PCR) Subject who participated in the canSEROcov study with a positive serology result Subject who gave his consent to this study Subject affiliated to a social security scheme  Group 3  Patient over 18 years of age treated in Oncology at the GF Leclerc center for:  Metastatic colorectal cancer beyond the first line of treatment Metastatic pancreatic cancer as the first line of treatment Metastatic breast cancer treated with anti-CDK4 / 6 + hormone therapy, or localized breast cancer treated with (neo) adjuvant chemotherapy Patient vaccinated against SARS-CoV-2 for at least 1 month (last injection), AND less than 4 months (last injection) with a vaccination performed when the anti-cancer treatment had been started for at least 1 month (last injection) ) (see diagram below) Patient having signed the informed consent for the study Patient affiliated to the social security scheme  Exclusion Criteria:  Groups 1, 2 and 3  Minor or under legal protection Person deprived of liberty or under guardianship (including curatorship) Inability to undergo medical monitoring of the trial for geographical, social or psychological reasons (filling in the questionnaire and taking the blood sample) Refusal of the patient or employee to participate pregnant or breastfeeding woman