Symmetrical muscle pain in leg hamstring muscles/muscle pain in left and right hamstring; Pain; Received 3rd dose of Comirnaty (booster dose); difficulty bending down; stiffness in hamstring; still do not have the ability to stretch leg to a full extension; The initial safety information received was reporting only non-serious adverse drug reactions, Upon receipt of follow-up information on 16Dec2021, this case now contains serious adverse reactions. Information processed together.  This is a spontaneous report received from a contactable reporter(s) (Consumer or other non HCP). The reporter is the patient.  A 56-year-old male patient received bnt162b2 (COMIRNATY), via an unspecified route of administration, administered in arm left, administration date 27Nov2021 15:00 (Batch/Lot number: unknown) at the age of 56 years as dose 3 (booster), single for covid-19 immunization. The patient had no relevant medical history. There were no concomitant medications. Vaccination history included: Covid-19 vaccine (Dose 2, Manufacturer unknown), for Covid-19 immunization; Covid-19 vaccine (Dose 1, Manufacturer unknown), for Covid-19 immunization. The following information was reported: IMMUNISATION (disability) with onset 27Nov2021 15:00, outcome "unknown", described as "Received 3rd dose of Comirnaty (booster dose)"; MYALGIA (disability) with onset 28Nov2021, outcome "recovering", described as "Symmetrical muscle pain in leg hamstring muscles/muscle pain in left and right hamstring"; PAIN (non-serious) with onset 28Nov2021, outcome "recovered" (12Dec2021), described as "Pain"; MOVEMENT DISORDER (non-serious) with onset 2021, outcome "unknown", described as "difficulty bending down"; MUSCULOSKELETAL STIFFNESS (non-serious) with onset 2021, outcome "recovering", described as "stiffness in hamstring"; LIMB DISCOMFORT (non-serious) with onset 2021, outcome "unknown", described as "still do not have the ability to stretch leg to a full extension". The event "symmetrical muscle pain in leg hamstring muscles/muscle pain in left and right hamstring" was evaluated at the physician office visit. Therapeutic measures were taken as a result of myalgia, pain, movement disorder, musculoskeletal stiffness, limb discomfort. Additional information: The patient did not connect the pain to the vaccine until very recently as the muscles were often used in the patient's workouts and garden work. The patient took 2 ibuprofens for muscle pain of the patient in both left and right hamstrings in legs. The ibuprofen helped but did not completely eliminate the pain. Each morning, the muscle pain was noticeable, and the patient described it as if he has done a few hundred squats the day before. This has persisted every day since the patient received his booster dose, and not it has been over 2 weeks. The patient frequently takes ibuprofen every morning, as the day proceeds with the pain and stiffness in hamstring. The stiffness was reduced but did not disappeared. The patient still had no ability to stretch his legs to a full extension, which he was able to do before. The patient has no other symptoms from the booster. The patient had an appointment with the doctor on 16Dec2021 due to muscle pain.   The lot number for bnt162b2 was not provided and will be requested during follow up.