COVID-19 infection was confirmed by PCR test/had received two doses of the BNT162b2 (Pfizer-BioNTech) vaccine 6 months prior to the onset of her infection; COVID-19 infection was confirmed by PCR test/had received two doses of the BNT162b2 (Pfizer-BioNTech) vaccine 6 months prior to the onset of her infection; Altered smell and taste; Altered smell and taste; Fever; Chills; Body aches; Chest pressure; Fatigue; Hair loss; This is a spontaneous report received from non-contactable reporter(s) (Physician).  A 47 year-old female patient received bnt162b2 (BNT162B2), administration date 2021 (Batch/Lot number: unknown) as dose 1, single and administration date 2021 (Batch/Lot number: unknown) as dose 2, single for covid-19 immunisation. The patient's relevant medical history and concomitant medications were not reported. The following information was reported: COVID-19 (medically significant), DRUG INEFFECTIVE (medically significant), outcome "unknown" and all described as "COVID-19 infection was confirmed by PCR test/had received two doses of the BNT162b2 (Pfizer-BioNTech) vaccine 6 months prior to the onset of her infection"; PAROSMIA (non-serious), TASTE DISORDER (non-serious), outcome "recovered" and all described as "altered smell and taste"; PYREXIA (non-serious), outcome "recovered", described as "fever"; CHILLS (non-serious), outcome "recovered", described as "chills"; PAIN (non-serious), outcome "recovered", described as "body aches"; CHEST DISCOMFORT (non-serious), outcome "recovered", described as "chest pressure"; FATIGUE (non-serious), outcome "recovered", described as "fatigue"; ALOPECIA (non-serious), outcome "recovered", described as "hair loss". The patient underwent the following laboratory tests and procedures: body temperature: low grade; chest x-ray: unknown results; echocardiogram: unknown results; electrocardiogram: unknown results; fibrin d dimer: unknown results; full blood count: normal; metabolic function test: unknown results; n-terminal prohormone brain natriuretic peptide: unknown results; sars-cov-2 test: negative, notes: she tested negative for COVID-19 by antigen test; postive; thyroid function test: unknown results; troponin i: unknown results. Therapeutic measures were taken as a result of parosmia, taste disorder, pyrexia, chills, pain, chest discomfort, fatigue.   Clinical course: Patient was evaluated post-COVID clinic for 7 months of PASC symptoms. She developed acute COVID-19 infection in the summer of 2021 and had received two doses of the BNT162b2 (Pfizer-BioNTech) vaccine 6 months prior to the onset of her infection. Her acute symptoms included cough, sore throat, altered smell and taste, headache, fever, chills, body aches, chest pressure, and fatigue, which were managed with home care. COVID-19 infection was confirmed by PCR test. Most acute symptoms resolved after 48 hours, but over the next several months she continued to suffer severe fatigue, cognitive difficulties, post-exertional malaise, insomnia, tachycardia, chest pressure, and body aches resulting in significant functional debilitation and a leave of absence from work. She also experienced headaches and hair loss, both of which self-resolved.  Workup included normal complete blood count, complete metabolic panel, thyroid function tests, troponin I, NT-proBNP, D-Dimer, EKG, chest x-ray, and echocardiogram. Trials of different management strategies were generally ineffective, but she did have some gradual improvement with time until plateau at about 5 months post-infection. A few weeks prior to our initial consultation, the patient was potentially exposed to COVID-19 and developed new symptoms of headache, congestion, sore throat, low grade fever, sweats, and malaise. She tested negative for COVID-19 by antigen test but was started on a 5-day course of nirmatrelvir (300mg)-ritonavir (100mg) twice daily on day 3 by her primary care provider, given considerations of a potential false negative and her breakthrough infection history. Her acute flu-like symptoms had already begun to self-improve by day 3, but she noticed rapid improvement of her pre-existing PASC symptoms after taking the antivirals. By the time they saw her in PASC clinic, her PASC symptoms had resolved, and she reported being back at her normal, pre-COVID health status and function. This case is a cautionary tale that demonstrates PASC can still occur in vaccinated individuals who develop breakthrough COVID-19 infections. The symptomatology, prolonged duration, and functional debilitation experienced by this patient are similar to that seen in many unvaccinated individuals with PASC. They suspect that her initial infection was likely the delta variant of SARS-CoV-2 based on time frame, but studies are needed to elucidate PASC patterns with different variants and vaccines. Another interesting feature of this case is the timing of the patient's rapid PASC symptom resolution with administration of nirmatrelvir-ritonavir. This is correlative and a single case, but it raises interesting questions about persistent viral reservoir as a potential mechanism of disease as previously proposed and whether antivirals may have a role in PASC treatment, which highlight the need for rigorous mechanistic studies and well-designed clinical trials.  The lot number for bnt162b2 was not provided and will be requested during follow up.; Sender's Comments: As there is limited information in the case provided, the causal association between the reported events with the suspect drug BNT162B2 cannot be excluded. The case will be reassessed once new information is available.