Risk of Venous Thromboembolism After Covid-19 Vaccination

covid-19 vaccination and blood clot risk

Risk of Venous Thromboembolism After Covid-19 Vaccination

COVID-19 vaccinations in the United States are effective in preventing illness and hospitalization, yet concern over post-vaccination venous thromboembolism(VTE) risk has led to vaccine hesitancy. In this study published in the Journal of Thrombosis and Haemostatis, with a large cohort of COVID-19 vaccinated patients, no increased risk for acute VTE post-vaccination was identified for the authorized vaccines in the United States.

Key Findings:

  • A total of 792,010 patients with at least one COVID-19 vaccination were identified from November 1, 2020, to November 1, 2021. A total of 1,565 VTE events were identified in the 90 days before and after COVID-19 vaccination. There were 772 cases before vaccination, and 793 after vaccination. Among the 793 patients with VTE after COVID-19 vaccination, 489 had DVT (upper or lower extremity) and 426 had PE. The overall incidence rates (IR) of VTE were low, 4.1 per 1000 person-years (p-yrs) post-vaccination compared to 4.0 per 1000 p-yrs pre-vaccination.
  • The finding of a minor elevation in risk within a subgroup of young women receiving the Pfizer vaccine in the study appears to be the result of the increased risk associated with pregnancy and the postpartum state, as removal of these patients from the analysis eliminated significant differences in pre-versus post-vaccination risk in the cohort of younger women.
  • Current guidance from the Centers for Disease Control and Prevention recommend mRNA-based COVID-19 vaccines over the Janssen vaccine under most circumstances and they recommend avoidance of the Janssen vaccine in patients with a history of HIT and in anyone with history of VITT. Compared to previously published studies, the current study additionally evaluated VTE outcomes with the Janssen vaccine. Concerns regarding thrombotic risk even in the absence of frank thrombocytopenia with this vaccine escalated after rare reports of VITT. These results demonstrate no significant elevation in VTE risk with the Janssen vaccine in the post-vaccination 90 days compared to the pre-vaccination 90 days.

Read the full study.

Patient Resources:

Study citation:

Houghton DE, Wysokinski W, Casanegra AI, et al. Risk of venous thromboembolism after COVID-19 vaccination. J Thromb Haemost. 2022;00:1–7. doi:10.1111/jth.15725