key: cord-0931858-u70m3sws
authors: Famularo, Giuseppe
title: COVID-19 vaccines and thrombosis
date: 2021-10-12
journal: Intern Emerg Med
DOI: 10.1007/s11739-021-02823-8
sha: 0442bda3eeaf06e58786b9675385ef56c06d54ba
doc_id: 931858
cord_uid: u70m3sws

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cultures grew no pathogens, and procalcitonin was normal. A contrast-enhanced computed tomography (CT) showed splenomegaly (longitudinal diameter 14 cm) and thrombosis of the left renal vein. A thrombophilia screen, including resistance to activated protein C, protein C and S activity, antiphospholipid antibodies (cardiolipin, β2 glycoprotein, and lupus), and homocysteine, was normal. Meropenem and anticoagulant therapy with enoxaparin were started, the patient's condition improved, and he was apyrexial and free of symptoms on the 8th day of hospital stay. Enoxaparin was then switched to dabigatran (110 mg twice per day) and he was discharged on day 9th. At follow-up 1 month later, the patient was doing well, blood levels of CRP and D-dimer were normal, and imaging studies showed complete resolution of the left renal vein thrombosis and no new or progressive thrombosis.

Thrombosis of the left renal vein was diagnosed 4 weeks after this patient was given the second dose of the messenger RNA Covid-19 vaccine BNT 162b2. On consideration of clinical presentation, the timing of onset, the atypical location of thrombosis, and the absence of established risk factors for venous thromboembolism we assumed this unusual thrombotic event could have been linked with the BNT 162b2 vaccine. I acknowledge the patient's history of chronic autoimmune hepatitis and colon cancer could be confounding. However, clinical, laboratory, and imaging work-up did not show any evidence of active hepatitis or cancer relapse. Furthermore, renal vein thrombosis has not been consistently reported in patients with infections of the urinary tract. As a matter of fact, this patient had none of the established risk factors for renal vein thrombosis such as nephrotic syndrome, membranous glomerulonephritis, renal cell carcinoma, surgery, urological procedures, kidney transplantation, and abdominal trauma [2] . In addition, autoimmune hepatitis as well as other chronic liver disorders are not associated with renal vein thrombosis.

Case reports and small series have suggested a potential safety signal associated with adenoviral vector Covid-19 vaccines involving venous thrombosis and thrombocytopenia (vaccine-induced immune thrombotic thrombocytopenia, VITT [3] [4] [5] . Of note, VITT was easily ruled out in this patient since he had normal platelet count at presentation and throughout the subsequent course and there was no evidence of multifocal thrombosis of the splanchnic and cerebral veins. Even though vaccine-induced inflammation and immune activation may underlie a definite thrombotic risk, it remains unclear whether Covid-19 vaccines could cause a clinically relevant prothrombotic state and what vaccinespecific factors could be contributing to. As of today, however, it is clear that Covid-19 vaccines as such could not be recognized as a risk factor for thromboembolic disease. However, this case is of concern and continued monitoring is needed to further assess any possible thrombotic signal.

Funding None.

Data availability All data are fully available.

The author declares that he has no conflict of interest.

Human and animal rights All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.

Informed consent For this type of study, formal consent is not required.

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