This is an observational study that will prospectively record and monitor responses and clinical outcomes of patients with cancer after covid-19 vaccination, including measurements of antibody titers in serum and also record potential factors that affect immunity, such as type and stage of cancer, type and time of systemic therapy in relation to covid-19 vaccination.

It is well recognised that patients with cancer are at an increased risk of severe COVID-19 disease and should be at high prioritisation for vaccination against SARS-CoV-2. In Greece the vaccination of healthcare workers has been initiated in January 2021, elderly citizens as well and for cancer patients of all ages will be initiated early February 2021. There are very little available data on the efficacy of immunisation with vaccines overall in cancer patients, with most existing data involving the influenza vaccine. The covid-19 vaccine trials have not included cancer patients, therefore, the efficacy and duration of immunity in patients with cancer are still unknown. Those patients are often immunocompromised due to their disease or the side-effects of their treatment.

Based on the above this study was designed to prospectively record and monitor patients with cancer after covid-19 vaccination. The study will record and measure clinical outcomes, such as possible infection from covid-19 despite vaccination, severity and mortality, but also possible side effects post vaccination. Within the study serological responses (IgG antibody titers) will also be monitored in three timepoints (prior to vaccination, one month and three months after completion of the two doses of vaccination). Potential factors that affect immunity, will be recorded, such as type and stage of cancer, type and time of systemic therapy in relation to covid-19 vaccination.

Inclusion Criteria:

• Patients with solid tumours and potentially immunocompromised, ie. currently with active disease and/or undergoing active antineoplastic therapy of any type (chemotherapy, immunotherapy, biologic therapy, targeted therapy) that will be vaccinated for covid-19 within the National Program of Vaccination
• patients must sign informed consent for their data monitoring and also for serum antibody titers to covid-19 vaccination measured in three timepoints, prior to 1st dose and 1 and 3 months post completion of two doses

Exclusion Criteria:

• patients with haematological malignancies are excluded
• patients with prior diagnosis of cancer and now on follow-up without active disease are excluded
• patients on adjuvant hormonal therapy are excluded

Patients with solid tumours and potentially immunocompromised, ie. currently with active disease and/or undergoing active antineoplastic therapy of any type (chemotherapy, immunotherapy, biologic therapy, targeted therapy) that will be vaccinated for covid-19 within the National Program of Vaccination.

Also a group of healthy volunteers from the hospital personnel that have been vaccinated within the National Program of Vaccination and signed informed consent for 3 measurements of antibody titers in serum, at the timepoints described aboved.