This is a literature report for the following literature source(s): "Effect of oral nirmatrelvir on Long COVID symptoms: a case series", Research Square [Preprint Server], 2022. A 42-year-old male patient received BNT162b2 (BNT162B2), as dose number 1, single (Batch/Lot number: unknown), as dose number 2, single (Batch/Lot number: unknown) and as dose number 3 (booster), single (Batch/Lot number: unknown) for Covid-19 immunisation. The patient's relevant medical history included: "rhinorrhea" (unspecified if ongoing), notes: Date: 2022, persisted for approximately 10 days.; "pharyngitis" (unspecified if ongoing), notes: Date: 2022, persisted for approximately 10 days.; "fatigue" (unspecified if ongoing), notes: Date: 2022, persisted for approximately 10 days.; "myalgia" (unspecified if ongoing), notes: Date: 2022, persisted for approximately 10 days.; "pruritic rash on his upper extremities" (unspecified if ongoing), notes: Date: 2022, persisted for approximately 10 days.; "groin" (unspecified if ongoing), notes: Date: 2022, persisted for approximately 10 days. The patient's concomitant medications were not reported. The following information was reported: VACCINATION FAILURE (medically significant), outcome "unknown", described as "A SARS-CoV-2 antigen test was positive"; COVID-19 (medically significant), outcome "unknown", described as "re-infection with SARS-CoV-2". The patient underwent the following laboratory tests and procedures: Chest X-ray: showed no abnormalities; Laboratory test: 25 ng/ml, notes: vitamin D insufficiency; SARS-CoV-2 test: positive; negative, notes: On Day 11; negative. Therapeutic measures were taken as a result of vaccination failure, Covid-19. Additional information: A 42-year-old man with no significant medical history developed rhinorrhoea and pharyngitis in early 2022, followed by fatigue, myalgia, and a pruritic rash on his upper extremities and groin that persisted for approximately 10 days. He had previously received 3 doses of the Pfizer-BioNTech SARS-CoV-2 vaccine, most recently 2 months prior. A SARS-CoV-2 antigen test was positive when performed two days after symptom onset; multiple additional antigen tests were subsequently positive. On Day 11, an antigen test was negative, and all of his symptoms resolved. Approximately two weeks later, he experienced new onset of severe myalgia and bone pain across his upper body, which he described as post-exertional soreness in the absence of exertion. There was an associated increase in fatigue, as well as heightened awareness of breathing (described as "lung soreness"). These symptoms persisted, and he contacted his primary care doctor for evaluation approximately 10 days later. At this visit, he noted that he was experiencing ongoing fatigue, and described being at 80% of his pre-COVID baseline health. Laboratory testing was notable only for vitamin D insufficiency (25 ng/mL); a chest X-ray showed no abnormalities. Approximately 7 weeks following initial symptom onset, his symptoms worsened. He experienced ongoing myalgia, severe fatigue, post-exertional malaise, and trouble with concentration ("brain fog"). These symptoms profoundly impacted his ability to perform his activities of daily living, and he felt substantially debilitated, reporting that he was at 4050% of his pre-COVID baseline health and that he was spending the majority of the day resting. He began to seek care for Long COVID because he was concerned about the duration for which his symptoms had persisted. As his symptoms continued to worsen, he was re-exposed to SARS-CoV-2 when his spouse and children tested positive on antigen tests. A repeat antigen test was negative, but he experienced further worsening of his symptoms which his provider attributed to possible re-infection with SARS-CoV-2. In this context, he received a prescription for nirmatrelvir/ ritonavir. Within days of re-exposure, the patient began to note an improvement in his persistent symptoms, while his family members continued to experience worsening symptoms. After symptomatic improvement for 1-2 days, he initiated a 5-day course of nirmatrelvir/ ritonavir. During this period, he continued to experience improvement in his symptoms. While they have not resolved entirely, he reports that he is gradually approaching his baseline health. No follow-up attempts are possible; information about lot/batch number cannot be obtained. No further information is expected. Sender's Comments: Based on the current limited available information and the drug-event temporal association, a possible contributory role of the suspect product BNT162B2 to the development of events Drug Ineffective and COVID-19 cannot be excluded.