Venous Thromboembolism after Moderna COVID-19 Vaccination: A Case Report

Background

The Moderna COVID-19 vaccine was approved in December 2020 after it was proven safe and highly effective in preventing symptomatic COVID-19 infection. Later, several cases reported the incidence of thrombosis and thrombocytopenia after the vaccine, which raised some concerns about its safety on the long-term. We aimed to report a case of a patient who developed extensive pulmonary embolism (PE) and deep vein thrombosis (DVT) after 18 days of receiving the second dose of Moderna COVID-19 vaccine.

Case presentation

A 32-years old Bangladeshi male, not known to have chronic illness, presented to the hospital with productive cough, subjective fever, excessive sweating, and occasional hemoptysis for 18 days, which all started 1 day after receiving his second dose of Moderna COVID-19 vaccine. Upon presentation, he was critically ill, hypoxic, tachypneic, and tachycardiac. Given the history of recent vaccination, with the presenting symptoms and elevated D-dimer level of 4.59 mg/L, pulmonary embolism was suspected, so urgent computed tomography pulmonary angiogram was done and indicated acute PE (Figure1). Furthermore, lower limb ultrasound doppler showed findings suggestive of acute DVT; though, serial complete blood counts showed no evidence of thrombocytopenia neither at presentation nor after that.

Discussion

Vaccine-induced thrombosis and thrombocytopenia have been reported previously in healthy individuals after receiving adenovirus-based SARS-CoV-2 vaccines. They were mostly occurring 5 to 30 days after vaccine administration. A previous case report described thrombosis and thrombocytopenia that developed after m-RNA vaccine (Moderna); however, our case reported thrombosis without thrombocytopenia after Moderna COVID-19 vaccination. Generally, it is difficult to establish a direct association between this serious thrombotic event and exposure to the Moderna COVID-19 vaccine from few case reports among millions of vaccine doses administered globally.

Conclusion

This case described the possible link between Moderna vaccine and venous thromboembolism; yet further evidence is needed to confirm this association.