BLOOD CLOT IN LEFT LUNG; SHORTNESS OF BREATH; DIARRHEA; LEG PAIN; INJECTION SITE PAIN; HEADACHE; SWEATING; DIZZINESS/FEELING FAINT; This spontaneous self-report was received from a patient and concerned a 29 year old female. The patient's height and weight were not reported. The patient's concurrent conditions included hypertension, latex allergy, allergic to banana, and non smoker.  The patient received Covid-19 vaccine ad26.cov2.s (suspension for injection, route of administration not reported, batch number: 205A21A expiry: UNKNOWN) dose was not reported, 1 total dose on left arm administered on 08-APR-2021 (Thursday) for prophylactic vaccination. Concomitant medications included labetalol and nifedipine for hypertension.  On 08-APR-2021, when patient received a vaccination it hurt at the time of injection. Later, she developed a headache. At night, she woke up with sweating. She went down to the kitchen and felt shortness of breath and felt faint. On 09-Apr-2021 (Friday), after she woke up, she developed diarrhea all day. On 10-APR-2021 (Saturday), her symptoms were continuing included diarrhea, sweating, dizziness, legs hurting, headache, and feeling shortness of breath. On 11-APR-2021 (Sunday), she felt better, however headache was ongoing. At night, she started feeling bad again. On 12-APR-2021, she woke up with diarrhea and sweating, no symptoms have resolved. On 13-APR-2021, her legs continued to be in pain. At night, she went to emergency room (ER) and have blood work done, showing it was positive for a blood clot. Her computerized axial tomography (CAT) was performed and blood clot in left lung was found. Her doctor said that all other blood work came back normal, and he did not see anything else wrong with her, and that the blood clot was related to the vaccine. He wanted to put her on a blood thinner and prescribed Eliquis (apixaban). Doctor mentioned that if she felt shortness of breath or started feeling dizzy, she must go to the hospital. It was reported that she was hospitalized for 1 day, and both admission and discharge dates were reported 13-APR-2021. The action taken with covid-19 vaccine ad26.cov2.s was not applicable. The patient was recovering from blood clot in left lung, injection site pain, headache, sweating, shortness of breath, dizziness/feeling faint, leg pain, and diarrhea. This report was serious (Hospitalization Caused / Prolonged, and Other Medically Important Condition).; Sender's Comments: This is a 29 year old male patient, who experienced leg pain and noted to have blood clot in the left lung 1 day and 5 days, respectively, after receiving the COVID-19 vaccine ad26.cov2.s on the left arm. Height and weight not reported.  Patient has hypertension and is taking Labetalol and Nifedipine. Patient has history of allergy to latex and banana. Patient is not a smoker.  Few hours after receiving the vaccine, patient developed headache, sweating, dizziness and shortness of breath. The following day, patient had diarrhea and experienced leg pain, laterality not reported. The symptoms were persistent and, 5 days after the vaccine, patient sought consult at the Emergency Room (ER) where the CAT scan showed blood clot in left lung. Patient was prescribed with Apaxiban. The information provided precludes a meaningful medical assessment. Additional information requested.