Legs are swollen and could not walk, might be an allergic reaction to  his coronavirus disease (COVID) booster shot; Legs are swollen and could not walk, might be an allergic reaction to  his coronavirus disease (COVID) booster shot; Legs are swollen and could not walk, might be an allergic reaction to  his coronavirus disease (COVID) booster shot; This spontaneous case was reported by an other health care professional and describes the occurrence of PERIPHERAL SWELLING (Legs are swollen and could not walk, might be an allergic reaction to  his coronavirus disease (COVID) booster shot), GAIT DISTURBANCE (Legs are swollen and could not walk, might be an allergic reaction to  his coronavirus disease (COVID) booster shot) and ALLERGY TO VACCINE (Legs are swollen and could not walk, might be an allergic reaction to  his coronavirus disease (COVID) booster shot) in an 80-year-old male patient who received mRNA-1273 BIVALENT .222 (MODERNA COVID-19 VACCINE, BIVALENT (ORIGINAL AND OMICRON BA.4/BA.5)) for COVID-19 immunisation.    Co-suspect products included non-company products TREPROSTINIL SODIUM (TYVASO) for Pulmonary arterial hypertension and TREPROSTINIL for Pulmonary arterial hypertension.    Concurrent medical conditions included Pulmonary arterial hypertension (Primary pulmonary arterial hypertension). Concomitant products included MACITENTAN (OPSUMIT) for an unknown indication.   On 28-Feb-2023, the patient started TREPROSTINIL SODIUM (TYVASO) (Inhalation use) 32 microgram four times per day. On an unknown date, the patient received dose of mRNA-1273 BIVALENT .222 (MODERNA COVID-19 VACCINE, BIVALENT (ORIGINAL AND OMICRON BA.4/BA.5)) (unknown route) 1 dosage form and TREPROSTINIL (Inhalation use) Dry Powder, UNK µg. On 19-Mar-2023, the patient experienced PERIPHERAL SWELLING (Legs are swollen and could not walk, might be an allergic reaction to  his coronavirus disease (COVID) booster shot) (seriousness criterion hospitalization), GAIT DISTURBANCE (Legs are swollen and could not walk, might be an allergic reaction to  his coronavirus disease (COVID) booster shot) (seriousness criterion hospitalization) and ALLERGY TO VACCINE (Legs are swollen and could not walk, might be an allergic reaction to  his coronavirus disease (COVID) booster shot) (seriousness criterion hospitalization). The patient was hospitalized on 19-Mar-2023 due to ALLERGY TO VACCINE, GAIT DISTURBANCE and PERIPHERAL SWELLING. At the time of the report, PERIPHERAL SWELLING (Legs are swollen and could not walk, might be an allergic reaction to  his coronavirus disease (COVID) booster shot), GAIT DISTURBANCE (Legs are swollen and could not walk, might be an allergic reaction to  his coronavirus disease (COVID) booster shot) and ALLERGY TO VACCINE (Legs are swollen and could not walk, might be an allergic reaction to  his coronavirus disease (COVID) booster shot) outcome was unknown.        For mRNA-1273 BIVALENT .222 (MODERNA COVID-19 VACCINE, BIVALENT (ORIGINAL AND OMICRON BA.4/BA.5)) (Unknown), the reporter considered PERIPHERAL SWELLING (Legs are swollen and could not walk, might be an allergic reaction to  his coronavirus disease (COVID) booster shot), GAIT DISTURBANCE (Legs are swollen and could not walk, might be an allergic reaction to  his coronavirus disease (COVID) booster shot) and ALLERGY TO VACCINE (Legs are swollen and could not walk, might be an allergic reaction to  his coronavirus disease (COVID) booster shot) to be related.    The patient began therapy with Tyvaso DPI (treprostinil inhalation powder) delivered by Tyvaso dry powder inhaler, on 28-Feb-2023 for primary pulmonary arterial hypertension. On 19-Mar-2023, 20 days after initiating Tyvaso DPI, the patient was in the hospital due to legs were swollen and could not walk and it was reported that it might be an allergic reaction due to his COVID booster shot.  Action taken with Tyvaso DPI was not reported for the events of peripheral swelling, gait disturbance and allergy to vaccine.   The reporter's causality for the events of peripheral swelling, gait disturbance and allergy to vaccine with COVID-19 vaccine was considered to be possibly related.   The company has assessed the adverse events of peripheral swelling, gait disturbance and allergy to vaccine as not related to treprostinil inhalational powder and tyvaso DPI inhaler.   No treatment medication was provided.  Company comment: This spontaneous case concerns an 80-year-old male patient with medical history of Pulmonary arterial hypertension treated with Treprostinil, experienced the serious, unexpected events of peripheral swelling, gait disturbance and allergy to vaccine, that led to hospitalization. The events occurred 20 days after initiating Tyvaso DPI. The patient received a booster dose of mRNA-1273.222 (BA.4/BA.5). The vaccination date was not provided, thus, exact latency between vaccination and onset of the events could not be assessed. It was reported that 20 days after initiating Tyvaso DPI, the patient was in the hospital due to swollen legs, and he could not walk. It was reported that it might be an allergic reaction due to his coronavirus booster dose. Peripheral swelling and gait disturbance could be a consequence of the patient's medical history of pulmonary arterial hypertension, so, this could be a confounder. The co-suspect medication of Treprostinil could be a confounder for the events due to the temporal relationship. No further clinical information was provided for medical review. The benefit-risk relationship of mRNA-1273.222 (BA.4/BA.5) is not affected by this report.; Sender's Comments: This spontaneous case concerns an 80-year-old male patient with medical history of Pulmonary arterial hypertension treated with Treprostinil, experienced the serious, unexpected events of peripheral swelling, gait disturbance and allergy to vaccine, that led to hospitalization. The events occurred 20 days after initiating Tyvaso DPI. The patient received a booster dose of mRNA-1273.222 (BA.4/BA.5). The vaccination date was not provided, thus, exact latency between vaccination and onset of the events could not be assessed. It was reported that 20 days after initiating Tyvaso DPI, the patient was in the hospital due to swollen legs, and he could not walk. It was reported that it might be an allergic reaction due to his coronavirus booster dose. Peripheral swelling and gait disturbance could be a consequence of the patient's medical history of pulmonary arterial hypertension, so, this could be a confounder. The co-suspect medication of Treprostinil could be a confounder for the events due to the temporal relationship. No further clinical information was provided for medical review. The benefit-risk relationship of mRNA-1273.222 (BA.4/BA.5) is not affected by this report.