Full Vaccination Can Cut Risk of Outpatient COVID-Related VTE

The study covered in this summary was published on MedRxiv.org as a preprint and has not yet been peer reviewed.

Key Takeaways

  • In a UK Biobank cohort, ambulatory patients with mild COVID-19 were 20 times more likely to develop venous thromboembolism (VTE) in the 30 days after a positive SARS-CoV-2 test than a control population without COVID-19.

  • The risk was even more pronounced for unvaccinated people with COVID-19 and substantially attenuated for such people who had been fully vaccinated.

  • VTE was more likely to occur in older, male, and obese subjects.

  • Carriers of inherited thrombophilia had an additional doubled risk for post-COVID-19 VTE, compared with noncarriers.

  • There was no association between vaccination and VTE risk in uninfected control subjects.

Why This Matters

  • Severe COVID-19 has been shown to elevate the risk for VTE, but few studies have quantified that risk in ambulatory patients with mild COVID-19, whose numbers are increasing worldwide.

  • Identification of risk in ambulatory patients with mild COVID-19 could help inform the need for oral anticoagulation for VTE prophylaxis.

Study Design

  • A cohort of ambulatory patients with COVID-19 from the UK Biobank were followed to assess 30-day risk for VTE and compared, using propensity-score matching, with individuals without SARS-CoV-2 infection.

  • Associations between post-COVID VTE and age, sex, ethnicity, socio-economic status, obesity, vaccination status, and inherited thrombophilia status were examined in multivariate analyses.

Key Results

  • SARS-CoV-2 infection, compared with no infection, was associated with a nearly 20-fold increase in VTE risk (hazard ratio [HR], 19.49; 95% CI, 11.50 – 33.05).

  • The risk was much higher in unvaccinated patients (HR, 29.37; 95% CI, 15.11 – 57.08) and substantially less pronounced in fully vaccinated patients (HR 2.79; 95% CI, 0.82 – 9.54).

  • Older participants had a higher risk for VTE, which doubled for every 10-year increase in age (adjusted HR, 2.00; 95% CI, 1.61 – 2.47). Men were at higher risk than women (adjusted HR, 1.66; 95% CI, 1.28 – 2.15), and people with obesity were at a higher risk than those without (adjusted HR, 1.85; 95% CI, 1.29 – 2.64).

  • Vaccination with two doses was associated with a reduced risk for VTE related to COVID-19 (adjusted HR, 0.13; 95% CI, 0.06 – 0.28).

  • There was no association between vaccination status and VTE unrelated to COVID-19.

  • Inherited thrombophilia presented an elevated risk for VTE related to SARS-CoV-2 infection (adjusted HR, 2.05; 95% CI, 1.15 – 3.66).

  • The adjusted HR was 2.17 (95% CI, 1.13 – 4.15) for factor V Leiden carriers and 1.52 (95% CI, 0.48 – 4.79) for prothrombin G20210A carriers.

  • People with higher polygenic risk scores were at elevated risk for VTE (adjusted HR per one standard deviation increase score, 1.33; 95% CI, 1.11 – 1.59).


  • Participants likely had fewer underlying health conditions than the general population in the United Kingdom, and despite their outpatient status, their infections were more likely to be symptomatic and severe.

  • The analyses involved several strains of SARS-CoV-2, but novel variants such as Omicron were not represented.

Study Disclosures

  • The authors received funding from multiple public and private sources, and serve as consultants/advisors for several pharmaceutical companies. The research group received grants and advisory or speaker fees from Amgen, Astellas, AstraZeneca, Chiesi-Taylor, Johnson & Johnson, and UCB. Training programs at the senior author’s institution received support from Janssen. One author is a part-time employee of Novo Nordisk. Another author has participated in advisory boards for Gilead, MSD, ViiV Healthcare, Theratechnologies, and Lilly; and his institution has received research support from Gilead, Merck Sharp and Dohme, ViiV Healthcare.

This is a summary of a preprint research study, Venous thromboembolism in ambulatory COVID-19 patients: clinical and genetic determinants, written by JQ Xie, from the Centre for Statistics in Medicine and NIHR Biomedical Research Centre Oxford, NDORMS, University of Oxford, United Kingdom, and colleagues on MedRxiv.org provided to you by Medscape. This study has not yet been peer reviewed. The full text of the study can be found on MedRxiv.org.

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