COLLAPSED; RIGHT LEG SWOLLEN; COULDN'T WALK WITHOUT PAIN IN RIGHT SIDE; PAIN; WEAKNESS; SERIOUSLY DISABLED; This spontaneous report received from a patient concerned a 77 year old, male. The patient's height, and weight were not reported. The patient's past medical history included: left knee replacement (13 years ago on 07-OCT-2010), and concurrent conditions included: diabetic(since 1970), penicillin allergy (real sick and could die from it), drug allergy (metformin allergy (started taking it years ago before Januvia, and had a serious blood reaction in system), blood pressure, and cholesterol. The patient received covid-19 vaccine ad26.cov2.s (suspension for injection, route of admin not reported, batch number: 1805025, expiry: UNKNOWN) dose was not reported, 1 total administered on left arm on 11-MAR-2021 for covid-19 prophylaxis. Age at time of vaccination 77 years old. Concomitant medications included lisinopril for blood pressure, atorvastatin for cholesterol, sitagliptin phosphate for diabetes, buspirone for keeping calm, and acetylsalicylic acid.  On an unspecified day in APR-2021, about a month after the vaccination, patient developed a critical reaction. Ever since then patient had become seriously disabled, and as time had gone by, it had gotten worse. The patient noted that he had discussed this with his doctors, but no one had been able to help him because whatever was in the injection had caused him a breakdown. The patient had tried using medications to subdue the pain. The patient said nothing had been able to relieve his pain. The patient described his right leg was swollen extremely large. The patient was concerned about how serious the reaction may get down the road since he was disabled and using a walker every day. The patient gets so weak he had to be careful not to hit the ground. The patient favors his right leg because his left knee was replaced 13 years ago. The patient said he had a serious condition on his left side. When this happened, his right leg was supporting his whole body. The patient shared, about one month after the vaccine, the weakness he had got to the point where he could not walk without pain in his right side. The patient stated he would be mowing grass and then would collapse. The patient commented he could not even go on the lawn because the last time he fell, he would have wound up in the hospital if he had not been able to get assistance from his neighbors. The action taken with covid-19 vaccine ad26.cov2.s was not applicable. The patient had not recovered from right leg swollen, weakness, couldn't walk without pain in right side, pain, and seriously disabled, and the outcome of collapsed was not reported. This report was serious (Other Medically Important Condition).; Sender's Comments: V0: 20230941662-seriously disabled. The event has a compatible/suggestive temporal relationship, is unlabeled, and has unknown scientific plausibility. There is no information on any other factors potentially associated with the event. Therefore, the WHO Causality is considered indeterminate. The company causality is considered unassessable. 20230941662-collapsed. The event has an unknown/unclear temporal relationship, is unlabeled, and has unknown scientific plausibility. There is no information on any other factors potentially associated with the event. Therefore, the WHO Causality is considered indeterminate. The company causality is considered unassessable.