platelets have been significantly dropping/platelets were down to 4,000 units; platelets have been significantly dropping/platelets were down to 4,000 units; Really Weak; This is a spontaneous report from a contactable consumer (patient's daughter). A 70-year-old female patient received the second dose of BNT162B2 (PFIZER-BIONTECH COVID-19 VACCINE, solution for injection), via an unspecified route of administration on 16Mar2021 (Batch/Lot number was not reported) at a single dose for COVID-19 immunization. Medical history included ongoing thrombocytopenia  (diagnosed 4-5 years ago). No concomitant medications. Family medical history included high cholesterol. The patient previously received the first vaccine dose of BNT162B2 on 23Feb2021 for COVID-19 immunization. No adverse event (AE) following prior vaccinations. The patient's daughter stated that the patient seemed like she was having an adverse reaction since her second vaccination. The patient's daughter said that this started after her mother received the second dose of the Pfizer-BioNTech COVID-19 Vaccine last 16Mar2021. The patient's platelets have been significantly dropping. The patient was rushed to the hospital because platelets were down to 4,000 units. The patient had  thrombocytopenia but was managed well. The patient has Thrombocytopenia Disease and her hematologist recommended that she get the vaccine. Before the second vaccine, her platelets had been stable, not at normal range, but 78,000 to 71,000, which was normal for her. After the vaccine, the patient's platelet level has been significantly plummeting to single digits like 4,000 and then in a few hours shooting to 31,000 (in Mar2021). It was a consistent up and down for her. The patient was rushed to the hospital from her doctor's office and she was being admitted because her platelet level was down to 4,000 and she was getting a platelet transfusion. Ever since the patient got the vaccine, this started happening. Before, only once in a 3 year span, the patient's platelets dropped to 6,000 and now this is happening very often. The patient felt really weak for the last 2 days since 19Mar2021 (as reported) especially but it really started the same time as her platelets first dropped, so they took her to see the hematologist and fortunately they were able to get her in and did a complete blood count (CBC) and her platelets were down to 4,000 on 19Mar2021 (as reported). The treatment included Platelet Transfusions and was given steroid medication (they haven't received it yet but she was prescribed Promacta by Novartis). The patient has been in and out of the hospital 3 times within 2 weeks. Within a 2 week time frame, the patient has been there 3 times, 2 direct admit hospitalizations and 1 emergency room (ER) visit. She was rushed to the ER on either 05Apr2021 or 06Apr2021, but she was not admitted because when they took her labs at the doctor, her platelets were 4,000, but when they were rechecked in the ER they were 38,000 so the released her because it came up and was over 30,000. The patient was admitted to the hospital from her doctor's office on 09Apr2021 and released 10Apr2021. She was admitted to the hospital again on 14Apr2021. Event occurred after the second vaccine dose. The patient had a visit to physician's office for a couple of times. The outcome of the events was not recovered.   Information on Lot/Batch number has been requested.