This is a Phase II study designed to investigate if the Covid 19 vaccines are capable of eliciting production of antibodies against S protein of Sar-S-Cov-2 virus among patients with medical history of cancer previously treated with monoclonal anti CD-20 antibodies. The antibody production is defined based on the detection of antibodies in the serologic Covid-19 rapid test against S protein or with semiquantitative assay when it becomes available.

Inclusion Criteria:

• All patients either diagnosed with cancer or with HIV positivity or treated with an antineoplastic regimen including anti CD-20 after Covid-19 vaccine will be registered on the study regardless of their type of cancer or type of antineoplastic regimen.
• Patients 21 years or older diagnosed with cancer treated with antineoplastic regimen or anti CD-20, or with HIV infection vaccinated with 2 doses of anti Covid-19 vaccine.
• Eligible patients will be registered on study after a Covid -19 vaccine has been scheduled.
• In order to be screened for Covid 19 antibodies, they must be tested at least two weeks after the second dose of Covid-19 vaccination.

Exclusion Criteria:

• Anyone who has not been treated with anti-CD20 antibodies or with chemotherapy who doesn't have HIV infection or who has not received chemotherapy for cancer.

All patients either diagnosed with cancer or with HIV positivity or treated with an antineoplastic regimen including anti CD-20 after Covid-19 vaccine.