current or recent cancer/ ovarian ca; weakened immune system; This is a spontaneous report received from a contactable reporter(s) (Consumer or other non HCP) from medical information team for a Pfizer sponsored program. The reporter is the patient.  A female patient received bnt162b2 (BNT162B2), intramuscular, administered in arm left, administration date 14Jul2021 10:30 (Lot number: FA6780) at the age of 60 years as dose 3 (booster), single for covid-19 immunisation. Relevant medical history included: "ovarian cancer", start date: 24Oct2018 (ongoing), notes: total hyst Nov2018 chemo 2019 and 2021; "hypertension", start date: 2018 (ongoing); "Reflux occasional" (ongoing), notes: Pepcid. Concomitant medication(s) included: LISINOPRIL [LISINOPRIL DIHYDRATE] taken for hypertension, start date: 2018. Past drug history included: Prednisone, start date: 04Jan2021, stop date: 01Jun2021, for ovarian cancer; Carboplatin, start date: 04Jan2021, stop date: 01Jun2021, for ovarian cancer; Doxetoxel, start date: 04Jan2021, stop date: 01Jun2021, for ovarian cancer. Vaccination history included: Bnt162b2 (Dose: 1, Date/Time (24hr): 24Jan2021 08:30, Anatomical site of injection: Left arm, Route of administration: Intramuscular, Batch/Lot number: EL3247), administration date: 24Jan2021, for COVID-19 immunization, reaction(s): "recurring ovarian cancer"; Bnt162b2 (Dose: 2, Date/Time (24hr): 14Feb2021 08:30, Anatomical site of injection: Left arm, Route of administration: Intramuscular, Batch/Lot number: EN6200), administration date: 14Feb2021, for COVID-19 immunization, reaction(s): "recurring ovarian cancer". The following information was reported: OVARIAN CANCER (medically significant), outcome "unknown", described as "current or recent cancer/ ovarian ca"; IMMUNE SYSTEM DISORDER (non-serious), outcome "unknown", described as "weakened immune system". The patient underwent the following laboratory tests and procedures: blood immunoglobulin g: (Mar2021) positive; (Apr2021) positive; (May2021) positive; investigation: (unspecified date) unknown results; (Jun2021) negative; (Jun2021) negative; (Jul2021) positive, notes: Received 4th 3rd dose-1 week later positive for antibody; (Dec2021) positive; sars-cov-2 test: (2021) negative, notes: conducted 2-5 days prior to six rounds of chemo from Jan2021-Jun2021.  Clinical course information: patient received Covid Pfizer series Jan/Feb2021. Antibody study she was enrolled showed no antibodies Jun2021. On my own, she went and got third shot Pfizer Jul2021.  she had 6 rounds of chemotherapy Jan-Jun2021 for recurring ovarian cancer. Dec2021 covid antibody test results were positive for IgG antibodies. There is no information about a fourth dose or a booster in immunocompromised patients and refer to HCP. Antibody test for Mar, Apr, and May 2021 showed antibodies. In Jun2021 there were no antibodies. She decided to get another dose. She states that she "got caught after". She tested positive for antibodies since then in Dec2021. She has spoken with her HCP who relayed to let her know when she would want to get another dose. patient asked that immune compromised patient has there been any data on essentially a 4th dose being needed or being effective? Does it protect against the Omicron variant? AE previously submitting in initial INT. AE-136766. E-transmitting for additional AE details. Female consumer. Age not captured. A third dose is not to be confused with a booster dose; booster dose is an additional dose of a vaccine that is given at least 6 months after completing the primary series because the immune response to the primary series wanes over time. 2,5 third dose) of the vaccine is given at least 4 weeks after the second dose to people who are determined to have certain kinds of immunocompromise and did not get an adequate immune response to the primary series. 2,5"The early results show that three doses of the Pfizer-BioNTech COVID-19 Vaccine neutralize the Omicron variant. Two doses of vaccine showed decreased antibody response. (7)"  No follow-up attempts are possible. No further information is expected.