I am obviously immunocompromized because of this history.; SARS COV 2 AB (IGG) Spike, SEMI QN-Det on 07Jul2021 resulted in a negative test/SARS-COV-2 SEROLOGY (COVID-19) ANTIBODY Test, which also came back negative; because of the Rituximab infusions the vaccines were not able to provide immunity against COVID -19.; The initial case was missing the following minimum criteria: adverse event. Upon receipt of follow-up information on 13Jan2022, this case now contains all required information to be considered valid.   This is a spontaneous report received from a contactable reporter(s) (Consumer or other non HCP) from medical information team. The reporter is the patient. Other Case identifier(s): US-PFIZER INC-202101878319 (Pfizer). A female patient received bnt162b2 (BNT162B2), administration date 31Mar2021 (Batch/Lot number: unknown) as dose 1, single, administration date 21Apr2021 (Batch/Lot number: unknown) as dose 2, single and administration date 22Sep2021 (Batch/Lot number: unknown) as dose 3 (booster), single for covid-19 immunisation; rituximab (RITUXIMAB), first regimen since 22Mar2021 (Batch/Lot number: unknown) at unk (last of these infusions) and second regimen since Mar2021 (Batch/Lot number: unknown) at unk (4 weekly infusions) for thrombocytopenia. Relevant medical history included: "Thrombocytopenia" (unspecified if ongoing). The patient's concomitant medications were not reported. The following information was reported: IMMUNODEFICIENCY (medically significant), outcome "unknown", described as "I am obviously immunocompromized because of this history."; SARS-COV-2 ANTIBODY TEST NEGATIVE (non-serious) with onset 07Jul2021, outcome "unknown", described as "SARS COV 2 AB (IGG) Spike, SEMI QN-Det on 07Jul2021 resulted in a negative test/SARS-COV-2 SEROLOGY (COVID-19) ANTIBODY Test, which also came back negative"; DRUG INTERACTION (non-serious) with onset Mar2021, outcome "unknown", described as "because of the Rituximab infusions the vaccines were not able to provide immunity against COVID -19.". The patient underwent the following laboratory tests and procedures: sars-cov-2 antibody test: (07Jul2021) negative, notes: had absolutely no antibodies; (unspecified date) negative, notes: which also came back negative. The action taken for rituximab was unknown.  Clinical course: The patient had inquired about receiving a 4th Pfizer vaccine. The reason for her request for a 4th vaccine was complicated, but simply put, back in Mar2021 she received 4 weekly infusions of rituximab for her thrombocytopenia disorder. The last of these infusions was on 22Mar2021. On 31Mar2021, she received her 1st Pfizer vaccine and on 21Apr2021 she received her 2nd Pfizer vaccine. It was mentioned that several weeks later she learned that because of the rituximab infusions the vaccines were not able to provide immunity against COVID-19. She had a SARS COV 2 AB (IGG) Spike, SEMI QN-Det on 07Jul2021 which resulted in a negative test. At that point she learned from her hematologist that rituximab stayed in the body for 6 months. Thus, the infusions negated the vaccines. So she waited the 6 months and received a Pfizer Booster shot on 22Sept2021 in hopes that would finally give her immunity to COVID-19. Though she should have had a 2nd Spike Protein Antibody test her physician ordered a SARS-COV-2 SEROLOGY (COVID-19) ANTIBODY Test, which also came back negative. This week when she met with her hematologist in (state) she sited a recent medical article that stated rituximab can remain in the body for 9 to 10 months. Thus, she stated that even the booster shot was ineffective as well. Therefore, she have been requesting with her healthcare physicians that she be allowed to have a 4th vaccine as she have zero immunity against any variants of COVID-19 because of the rituximab infusions. Their replies have been that she may not get a 4th vaccine because the FDA and CDC hasn't authorized it yet. She stated that she was am obviously immunocompromized because of this history. She queried how to go about having a 4th Pfizer vaccine. She stated that with the raging cases of the virus here in (State), she felt totally vulnerable.   The lot number for bnt162b2, rituximab was not provided and will be requested during follow up.