T-cell adaptive immunity is known to be required to sustain a long term immunoglobulin production and a long term memory against several infections. Previous results suggest a lack in the generation of T-cell responses against CoV-N, M and S proteins among cancer patients exposed to SARS-CoV-2 virus highlighting that cancer patients failed to mount a protective T-cell immunity. Given this context, our hypothesis is that COVID-19 vaccine candidates are not immunogenic in some cancer patients. Thus, the monitoring of CD4 and CD8 T-cell responses before and after vaccination might provide information related to the correlation between induction of CD4 T-cells (including helper follicular T-cells) by the vaccine and long-term IgG production (serological index). Additionally, the failure of COVID-19 vaccines in some patients should be monitor carefully in order to provide specific recommendations to avoid COVID-19 infections. The main objective is to assess humoral immune responses following COVID-19 vaccination in a population of cancer patients.

*Inclusion Criteria:

• Male or female patients
• Age ≥ 18 years
• Not having developed a symptomatic form of COVID-19 within the last 3 months before inclusion
• Eligible to the vaccination against SARS-CoV-2
• Affiliation to French social security or receiving such a regime,
• Signed informed consent
• Ability to comply with the study protocol, in the Investigator's judgment

Cancer patients

• Patients under active anticancer treatment: in adjuvant or neoadjuvant setting or in first line of treatment in metastatic setting. Except for prostate cancer (until metastatic castration-resistant prostate cancer); and breast cancer hormonal receptor positive/HER2 negative (until apparition of hormonal resistance).
• Patients in follow-up (active treatment < 3 months).

Elderly:

Age ≥ 70 years old

Healthy person:

Age ≥ 18 years old and < 70 years old

*Exclusion Criteria:

• Patient under guardianship, guardianship or under the protection of justice
• Receipt of a live, attenuated vaccine within 4 weeks prior to the initiation of treatment or anticipation that such a live, attenuated vaccine will be required during the study.

Patients vaccinated against COVID-19