Acute Extensive Deep Vein Thrombosis After Heterogeneous Administration of Moderna mRNA Booster Vaccine: A Case Report

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) struck the world in 2019 and led to the development of the multisystem coronavirus disease-2019 (COVID-19) causing a worldwide pandemic. Vaccines with boosters were developed due to novel mutations of SARS-CoV-2. Heterogeneous vaccination emerged with the perception that mixing vaccines can provide better protection. We present the case of a 68-year-old male patient who developed extensive acute deep vein thrombosis (DVT) of the left lower extremity, two weeks following the Moderna mRNA booster vaccine (mRNA-1273). His first two doses were AstraZeneca ChAdOx1-S [recombinant]. He was started on a heparin drip and prescribed rivaroxaban. We discuss the possible etiology of this DVT, the mechanism of action of the Moderna mRNA vaccine, the association of DVT with vaccine-induced inflammation, implications of heterogeneous vaccine combinations, and recommendations to advise people on possible thrombogenic adverse effects prior to mRNA vaccine administration.