The COVID-19 pandemic has a major impact at all stages of cancer treatment. Risk of death from COVID-19 in patients treated for a cancer is high. COVID-19 vaccines represent a major issue to decrease the rate of severe forms of the COVID-19 cases and to maintain a normal cancer care. It is difficult to define the target population for vaccination due to the limited data available and the lack of vaccine doses available. It appears theoretically important to vaccinate patients with active cancer treatment or treated since less than three years, as well as their family circle. In France, patients actually defined at "high risk" for priority access to vaccination are those with a cancer treated by chemotherapy. A panel of experts recently defined another "very high-priority" population, which includes patients with curative or palliative first or second-line chemotherapy, as well as patients requiring surgery or radiotherapy involving a large lung volume, lymph nodes and/or of hematopoietic tissue. Ideally, it is best to vaccinate before cancer treatment. Despite the lack of published data, COVID-19 vaccines can also be performed during chemotherapy by avoiding periods of bone marrow aplasia and if possible, to do it in cancer care centers. It is necessary to implement cohorts with immunological and clinical monitoring of vaccinated cancer patients. To conclude, considering the current state of knowledge, the benefit-risk ratio strongly favours COVID-19 vaccination of all cancer patients.