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Study Points to Increased Risk of Dangerous Blood Clots in COVID-19 Patients

An analysis of clinical and genetic risk factors associated with venous thromboembolism (VTE) in ambulatory COVID-19 patients is published in JAMA Internal Medicine this week, revealing that even mild disease substantially increases the risk of incident VTE. While VTE has been linked to severe COVID-19, the association between these blood clots and milder COVID-19 remains controversial. To investigate, a team led by University of Oxford scientists performed a retrospective cohort study of 18,818 COVID-19 outpatients and 93,179 propensity score-matched noninfected individuals. The researchers find SARS-CoV-2 infection in this patient population was associated with an increased risk of VTE in 30 days, although this risk was substantially attenuated among those who were fully vaccinated. Additional factors increasing VTE risk included older age, male sex, obesity, and factor V Leiden thrombophilia. The findings, the study's authors write, "may reinforce the need for vaccination, inform VTE risk stratification, and call for targeted VTE prophylaxis strategies for unvaccinated outpatients with COVID-19."